Merge Sunil Shetye's --limitflush patch.

[~andy/fetchmail] / fetchmail.man

'\" t
.\" ** The above line should force tbl to be used as a preprocessor **
.\"
.\" Manual page in man(7) format with tbl(1) macros for fetchmail
.\"
.\" For license terms, see the file COPYING in this directory.
.\"
.TH fetchmail 1
.SH NAME
fetchmail \- fetch mail from a POP, IMAP, ETRN, or ODMR-capable server

.SH SYNOPSIS
\fBfetchmail\fR [\fIoption...\fR] [\fImailserver...\fR]
.br
\fBfetchmailconf\fR

.SH DESCRIPTION
.I fetchmail
is a mail-retrieval and forwarding utility; it fetches mail from
remote mailservers and forwards it to your local (client) machine's
delivery system.  You can then handle the retrieved mail using normal
mail user agents such as \fImutt\fR(1), \fIelm\fR(1) or \fIMail\fR(1).
The \fIfetchmail\fR utility can be run in a daemon mode to repeatedly
poll one or more systems at a specified interval.
.PP
The
.I fetchmail
program can gather mail from servers supporting any of the common
mail-retrieval protocols: POP2, POP3, IMAP2bis, IMAP4, and IMAP4rev1.
It can also use the ESMTP ETRN extension and ODMR.  (The RFCs describing all
these protocols are listed at the end of this manual page.)
.PP
While
.I fetchmail
is primarily intended to be used over on-demand TCP/IP links (such as
SLIP or PPP connections), it may also be useful as a message transfer
agent for sites which refuse for security reasons to permit
(sender-initiated) SMTP transactions with sendmail.
.PP
If
.I fetchmail
is used with a POP or an IMAP server, it has two fundamental modes of
operation for each user account from which it retrieves mail:
\fIsingledrop\fR- and \fImultidrop\fR-mode.  In singledrop-mode,
.I fetchmail
assumes that all messages in the user's account are intended for a single
recipient.  An individual mail message will not be inspected for recipient
information, rather, the identity of the recipient will either default to
the local user currently executing \fIfetchmail\fR,
or else will need to be explicitly specified in the configuration file.
Singledrop-mode is used when the fetchmailrc configuration contains at
most a single local user specification for a given server account.
.PP
With multidrop-mode,
.I fetchmail
is not able to assume that there is only a single recipient, but rather
that the mail server account actually contains mail intended for any
number of different recipients.  Therefore,
.I fetchmail
must attempt to deduce the proper "envelope recipient" from the mail
headers of each message.  In this mode of operation
.I fetchmail
almost resembles an MTA, however it is important to note that neither
the POP nor IMAP protocols were intended for use in this fashion, and
hence envelope information is not directly available.  Instead,
.I fetchmail
must resort to a process of informed guess-work in an attempt to
discover the true envelope recipient of a message.  Even if this
information is present in the headers, the process can
be error-prone and is dependent upon the specific mail server used
for mail retrieval.  Multidrop-mode is used when more than one local
user is specified for a particular server account in the configuration
file.  Note that the forgoing discussion of singledrop- and
multidrop-modes does not apply to the ESMTP ETRN or ODMR retrieval
methods, since they are based upon the SMTP protocol which
specifically provides the envelope recipient to \fIfetchmail\fR.
.PP
As each message is retrieved \fIfetchmail\fR normally delivers it via SMTP to
port 25 on the machine it is running on (localhost), just as though it
were being passed in over a normal TCP/IP link.  \fIfetchmail\fR provides
the SMTP server with an envelope recipient derived in the manner described
previously.  The mail will then be
delivered locally via your system's MDA (Mail Delivery Agent, usually
\fIsendmail\fR(8) but your system may use a different one such
as \fIsmail\fR, \fImmdf\fR, \fIexim\fR, \fIpostfix\fR, or \fIqmail\fR).  All the
delivery-control mechanisms (such as \fI.forward\fR files) normally
available through your system MDA and local delivery agents will
therefore work automatically.
.PP
If no port 25 listener is available, but your fetchmail configuration
was told about a reliable local MDA, it will use that MDA for local
delivery instead.
.PP
If the program
.I fetchmailconf
is available, it will assist you in setting up and editing a
fetchmailrc configuration.  It runs under the X window system and
requires that the language Python and the Tk toolkit be present on your
system.  If you are first setting up fetchmail for single-user mode, it
is recommended that you use Novice mode.  Expert mode provides complete
control of fetchmail configuration, including the multidrop features.
In either case, the 'Autoprobe' button will tell you the most capable
protocol a given mailserver supports, and warn you of potential problems
with that server.

.SH GENERAL OPERATION
The behavior of
.I fetchmail
is controlled by command-line options and a run control file,
.IR ~/.fetchmailrc\fR ,
the syntax of which we describe in a later section (this file is what
the \fIfetchmailconf\fR program edits).  Command-line options override
.I ~/.fetchmailrc
declarations.
.PP
Each server name that you specify following the options on the
command line will be queried.  If you don't specify any servers
on the command line, each 'poll' entry in your
.I ~/.fetchmailrc
file will be queried.
.PP
To facilitate the use of
.I fetchmail
in scripts and pipelines, it returns an appropriate exit code upon
termination -- see EXIT CODES below.
.PP
The following options modify the behavior of \fIfetchmail\fR.  It is
seldom necessary to specify any of these once you have a
working \fI.fetchmailrc\fR file set up.
.PP
Almost all options have a corresponding keyword which can be used to
declare them in a
.I .fetchmailrc
file.
.PP
Some special options are not covered here, but are documented instead
in sections on AUTHENTICATION and DAEMON MODE which follow.
.SS General Options
.TP
.B \-V | \-\-version
Displays the version information for your copy of
.IR fetchmail .
No mail fetch is performed.
Instead, for each server specified, all the option information
that would be computed if
.I fetchmail
were connecting to that server is displayed.  Any non-printables in
passwords or other string names are shown as backslashed C-like
escape sequences.  This option is useful for verifying that your
options are set the way you want them.
.TP
.B \-c | \-\-check
Return a status code to indicate whether there is mail waiting,
without actually fetching or deleting mail (see EXIT CODES below).
This option turns off daemon mode (in which it would be useless).  It
doesn't play well with queries to multiple sites, and doesn't work
with ETRN or ODMR.  It will return a false positive if you leave read but
undeleted mail in your server mailbox and your fetch protocol can't
tell kept messages from new ones.  This means it will work with IMAP,
not work with POP2, and may occasionally flake out under POP3.
.TP
.B \-s | \-\-silent
Silent mode.  Suppresses all progress/status messages that are
normally echoed to standard output during a fetch (but does not
suppress actual error messages).  The --verbose option overrides this.
.TP
.B \-v | \-\-verbose
Verbose mode.  All control messages passed between
.I fetchmail
and the mailserver are echoed to stdout.  Overrides --silent.
Doubling this option (-v -v) causes extra diagnostic information
to be printed.
.SS Disposal Options
.TP
.B \-a | \-\-all
(Keyword: fetchall)
Retrieve both old (seen) and new messages from the mailserver.  The
default is to fetch only messages the server has not marked seen.
Under POP3, this option also forces the use of RETR rather than TOP.
Note that POP2 retrieval behaves as though --all is always on (see
RETRIEVAL FAILURE MODES below) and this option does not work with ETRN
or ODMR.
.TP
.B \-k | \-\-keep
(Keyword: keep)
Keep retrieved messages on the remote mailserver.  Normally, messages
are deleted from the folder on the mailserver after they have been retrieved.
Specifying the
.B keep
option causes retrieved messages to remain in your folder on the
mailserver.  This option does not work with ETRN or ODMR.
.TP
.B \-K | \-\-nokeep
(Keyword: nokeep)
Delete retrieved messages from the remote mailserver.  This
option forces retrieved mail to be deleted.  It may be useful if
you have specified a default of \fBkeep\fR in your
\&\fI.fetchmailrc\fR.  This option is forced on with ETRN and ODMR.
.TP
.B \-F | \-\-flush
POP3/IMAP only.  This is a dangerous option and can cause mail loss when
used improperly. It deletes old (seen) messages from the mailserver
before retrieving new messages.  Warning: This can cause mail loss if
you check your mail with other clients than fetchmail, and cause
fetchmail to delete a message it had never fetched before. Similarly, if
your local MTA hangs and fetchmail is aborted, the next time you run
fetchmail, it will delete mail that was never delivered to you.  You
should probably not use this option in your configuration file. What you
probably want is the default setting: if you don't specify '-k', then
fetchmail will automatically delete messages after successful
delivery. This option does not work with ETRN and ODMR.
.TP
.B \-\-limitflush
POP3/IMAP only.  Delete oversized messages from the
mailserver before retrieving new messages. The size limit should be
separately sepecified with the --limit option.  This option does not
work with ETRN or ODMR.
.SS Protocol and Query Options
.TP
.B \-p <proto> | \-\-protocol <proto>
(Keyword: proto[col])
Specify the protocol to use when communicating with the remote
mailserver.  If no protocol is specified, the default is AUTO.
.I proto
may be one of the following:
.RS
.IP AUTO
Tries IMAP, POP3, and POP2 (skipping any of these for which support
has not been compiled in).
.IP POP2
Post Office Protocol 2
.IP POP3
Post Office Protocol 3
.IP APOP
Use POP3 with old-fashioned MD5-challenge authentication.
.IP RPOP
Use POP3 with RPOP authentication.
.IP KPOP
Use POP3 with Kerberos V4 authentication on port 1109.
.IP SDPS
Use POP3 with Demon Internet's SDPS extensions.
.IP IMAP
IMAP2bis, IMAP4, or IMAP4rev1 (\fIfetchmail\fR autodetects their capabilities).
.IP ETRN
Use the ESMTP ETRN option.
.IP ODMR
Use the the On-Demand Mail Relay ESMTP profile.
.RE
.P
All these alternatives work in basically the same way (communicating
with standard server daemons to fetch mail already delivered to a
mailbox on the server) except ETRN and ODMR.  The ETRN mode
allows you to ask a compliant ESMTP server (such as BSD sendmail at
release 8.8.0 or higher) to immediately open a sender-SMTP connection
to your client machine and begin forwarding any items addressed to
your client machine in the server's queue of undelivered mail.   The
ODMR mode requires an ODMR-capable server and works similarly to
ETRN, except that it does not require the client machine to have
a static DNS.
.TP
.B \-U | \-\-uidl
(Keyword: uidl)
Force UIDL use (effective only with POP3).  Force client-side tracking
of 'newness' of messages (UIDL stands for "unique ID listing" and is
described in RFC1939).  Use with 'keep' to use a mailbox as a baby
news drop for a group of users. The fact that seen messages are skipped
is logged, unless error logging is done through syslog while running in
daemon mode.  Note that fetchmail may automatically enable this option
depending on upstream server capabilities.  Note also that this option
may be removed and forced enabled in a future fetchmail version.

.TP
.B \-P <portnumber> | \-\-port <portnumber>
(Keyword: port)
The port option permits you to specify a TCP/IP port to connect on.
This option will seldom be necessary as all the supported protocols have
well-established default port numbers. On some older machines, however,
the protocol <\-\-> port mappings are missing from the services database
(often /etc/services), and this port can make fetchmail work for you
even if you don't have system administrator privileges. See the FAQ item
R12 for details.
.TP
.B \-\-principal <principal>
(Keyword: principal)
The principal option permits you to specify a service principal for
mutual authentication.  This is applicable to POP3 or IMAP with Kerberos
authentication.
.TP
.B \-t <seconds> | \-\-timeout <seconds>
(Keyword: timeout)
The timeout option allows you to set a server-nonresponse
timeout in seconds.  If a mailserver does not send a greeting message
or respond to commands for the given number of seconds,
\fIfetchmail\fR will hang up on it.  Without such a timeout
\fIfetchmail\fR might hang up indefinitely trying to fetch mail from a
down host.  This would be particularly annoying for a \fIfetchmail\fR
running in background.  There is a default timeout which fetchmail\~-V
will report.  If a given connection receives too many timeouts in
succession, fetchmail will consider it wedged and stop retrying,
the calling user will be notified by email if this happens.
.TP
.B \-\-plugin <command>
(Keyword: plugin) The plugin option allows you to use an external
program to establish the TCP connection.  This is useful if you want
to use socks, SSL, ssh, or need some special firewalling setup.  The
program will be looked up in $PATH and can optionally be passed the
hostname and port as arguments using "%h" and "%p" respectively (note
that the interpolation logic is rather primitive, and these token must
be bounded by whitespace or beginning of string or end of string).
Fetchmail will write to the plugin's stdin and read from the plugin's
stdout.
.TP
.B \-\-plugout <command>
(Keyword: plugout)
Identical to the plugin option above, but this one is used for the SMTP
connections (which will probably not need it, so it has been separated
from plugin).
.TP
.B \-r <name> | \-\-folder <name>
(Keyword: folder[s])
Causes a specified non-default mail folder on the mailserver (or
comma-separated list of folders) to be retrieved.  The syntax of the
folder name is server-dependent.  This option is not available under
POP3, ETRN, or ODMR.
.TP
.B \-\-tracepolls
(Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'polling %s
account %s' to the Received line it generates, where the %s parts are
replaced by the user's remote name and the poll label (the Received
header also normally includes the server's true name).  This can be
used to facilitate mail filtering based on the account it is being
received from.
.TP
.B \-\-ssl
(Keyword: ssl)
Causes the connection to the mail server to be encrypted via SSL.  Connect
to the server using the specified base protocol over a connection secured
by SSL.  SSL support must be present at the server.  If no port is
specified, the connection is attempted to the well known port of the SSL
version of the base protocol.  This is generally a different port than the
port used by the base protocol.  For IMAP, this is port 143 for the clear
protocol and port 993 for the SSL secured protocol.
.TP
.B \-\-sslcert <name>
(Keyword: sslcert)
Specifies the file name of the client side public SSL certificate.  Some
SSL encrypted servers may require client side keys and certificates for
authentication.  In most cases, this is optional.  This specifies
the location of the public key certificate to be presented to the server
at the time the SSL session is established.  It is not required (but may
be provided) if the server does not require it.  Some servers may
require it, some servers may request it but not require it, and some
servers may not request it at all.  It may be the same file
as the private key (combined key and certificate file) but this is not
recommended.
.TP
.B \-\-sslkey <name>
(Keyword: sslkey)
Specifies the file name of the client side private SSL key.  Some SSL
encrypted servers may require client side keys and certificates for
authentication.  In most cases, this is optional.  This specifies
the location of the private key used to sign transactions with the server
at the time the SSL session is established.  It is not required (but may
be provided) if the server does not require it.  Some servers may
require it, some servers may request it but not require it, and some
servers may not request it at all.  It may be the same file
as the public key (combined key and certificate file) but this is not
recommended.  If a password is required to unlock the key, it will be
prompted for at the time just prior to establishing the session to the
server.  This can cause some complications in daemon mode.
.TP
.B \-\-sslproto <name>
(Keyword: sslproto)
Forces an SSL protocol. Possible values are '\fBssl2\fR',
\&'\fBssl3\fR', '\fBssl23\fR', and '\fBtls1\fR'. Try this if the default
handshake does not work for your server. To defeat automatic TLSv1
negotiation when the server advertises STARTTLS or STLS, use \fB''\fR or
\&'\fBssl23\fR'. The default is to try appropriate protocols depending
on context.
.TP
.B \-\-sslcertck
(Keyword: sslcertck)
Causes fetchmail to strictly check the server certificate against a set of
local trusted certificates (see the \fBsslcertpath\fR option). If the server
certificate is not signed by one of the trusted ones (directly or indirectly),
the SSL connection will fail. This checking should prevent man-in-the-middle
attacks against the SSL connection. Note that CRLs are seemingly not currently
supported by OpenSSL in certificate verification! Your system clock should
be reasonably accurate when using this option!
.TP
.B \-\-sslcertpath <directory>
(Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates. The default
is your OpenSSL default one. The directory must be hashed as OpenSSL expects
it - every time you add or modify a certificate in the directory, you need
to use the \fBc_rehash\fR tool (which comes with OpenSSL in the tools/
subdirectory).
.TP
.B \-\-sslfingerprint <fingerprint>
(Keyword: sslfingerprint)
Specify the fingerprint of the server key (an MD5 hash of the key) in
hexadecimal notation with colons separating groups of two digits. The letter
hex digits must be in upper case. This is the default format OpenSSL uses,
and the one fetchmail uses to report the fingerprint when an SSL connection
is established. When this is specified, fetchmail will compare the server key
fingerprint with the given one, and the connection will fail if they do not
match. This can be used to prevent man-in-the-middle attacks.
.SS Delivery Control Options
.TP
.B \-S <hosts> | \-\-smtphost <hosts>
(Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more
hostnames, comma-separated). Hosts are tried in list order; the first
one that is up becomes the forwarding target for the current run.
Normally, 'localhost' is added to the end of the list as an invisible
default.  However, when using Kerberos authentication, the FQDN of the
machine running fetchmail is added to the end of the list as an
invisible default. Each hostname may have a port number following the
host name.  The port number is separated from the host name by a
slash; the default port is 25 (or "smtp" under IPv6).  If you
specify an absolute path name (beginning with a /), it will be
interpreted as the name of a UNIX socket accepting LMTP connections
(such as is supported by the Cyrus IMAP daemon) Example:
.sp
.nf
        --smtphost server1,server2/2525,server3,/var/imap/socket/lmtp
.fi
.sp
This option can be used with ODMR, and will make fetchmail a relay
between the ODMR server and SMTP or LMTP receiver.
.TP
.B \-\-fetchdomains <hosts>
(Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains the
server should ship mail for once the connection is turned around.  The
default is the FQDN of the machine running
.IR fetchmail .
.TP
.B \-D <domain> | \-\-smtpaddress <domain>
(Keyword: smtpaddress) Specify the domain to be appended to addresses
in RCPT TO lines shipped to SMTP. The name of the SMTP server (as
specified by --smtphost, or defaulted to "localhost") is used when
this is not specified.
.TP
.B \-\-smtpname <user@domain>
(Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped to SMTP.
The default user is the current local user.
.TP
.B \-Z <nnn> | \-\-antispam <nnn[, nnn]...>
(Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be interpreted
as a spam-block response from the listener.  A value of -1 disables
this option.  For the command-line option, the list values should
be comma-separated.
.TP
.B \-m <command> | \-\-mda <command>
(Keyword: mda) You can force mail to be passed to an MDA directly
(rather than forwarded to port 25) with the --mda or -m option.  To
avoid losing mail, use this option only with MDAs like maildrop, procmail or
sendmail that return a nonzero status on disk-full and other
resource-exhaustion errors; the nonzero status tells fetchmail that
delivery failed and prevents the message from being deleted off the
server.  If \fIfetchmail\fR is running as root, it sets its user id to
that of the target user while delivering mail through an MDA.  Some
possible MDAs are "/usr/sbin/sendmail -i -f %F %T", "/usr/bin/deliver"
and "/usr/bin/procmail -d %T" (but the latter is usually redundant as
it's what SMTP listeners normally forward to).  Local delivery
addresses will be inserted into the MDA command wherever you place a
%T; the mail message's From address will be inserted where you place
an %F. \fBDO NOT ENCLOSE THE %F OR %T STRING IN SINGLE QUOTES!\fR For
both %T and %F, fetchmail encloses the addresses in single quotes ('),
after removing any single quotes they may contain, before the MDA
command is passed to the shell.  Do \fINOT\fR use an MDA invocation
like "sendmail -i -t" that dispatches on the contents of To/Cc/Bcc, it
will create mail loops and bring the just wrath of many postmasters
down upon your head.  Also, do \fInot\fR try to combine multidrop
mode with an MDA such as procmail that can only accept one address;
you will lose mail.
.TP
.B \-\-lmtp
(Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol).  A service
port \fImust\fR be explicitly specified (with a slash suffix) on each
host in the smtphost hunt list if this option is selected; the
default port 25 will (in accordance with RFC 2033) not be accepted.
.TP
.B \-\-bsmtp <filename>
(keyword: bsmtp)
Append fetched mail to a BSMTP file.  This simply contains the SMTP
commands that would normally be generated by fetchmail when passing
mail to an SMTP listener daemon.  An argument of '-' causes the mail
to be written to standard output.  Note that fetchmail's
reconstruction of MAIL FROM and RCPT TO lines is not guaranteed
correct; the caveats discussed under THE USE AND ABUSE OF MULTIDROP
MAILBOXES below apply.
.SS Resource Limit Control Options
.TP
.B \-l <maxbytes> | \-\-limit <maxbytes>
(Keyword: limit) Takes a maximum octet size argument.  Messages larger
than this size will not be fetched and will be left on the server (in
foreground sessions, the progress messages will note that they are
"oversized").  If the fetch protocol permits (in particular, under
IMAP or POP3 without the fetchall option) the message will not be
marked seen.
.sp
An explicit --limit of 0 overrides any limits set in your
run control file. This option is intended for those needing to
strictly control fetch time due to expensive and variable phone rates.
.sp
Combined with --limitflush, it can be used to delete oversized
messages waiting on a server.  In daemon mode, oversize notifications
are mailed to the calling user (see the --warnings option). This
option does not work with ETRN or ODMR.
.TP
.B \-w <interval> | \-\-warnings <interval>
(Keyword: warnings)
Takes an interval in seconds.  When you call
.I fetchmail
with a 'limit' option in daemon mode, this controls the interval at
which warnings about oversized messages are mailed to the calling user
(or the user specified by the 'postmaster' option).  One such
notification is always mailed at the end of the the first poll that
the oversized message is detected.  Thereafter, renotification is
suppressed until after the warning interval elapses (it will take
place at the end of the first following poll).
.TP
.B \-b <count> | \-\-batchlimit <count>
(Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to an SMTP
listener before the connection is deliberately torn down and rebuilt
(defaults to 0, meaning no limit).  An explicit --batchlimit of 0
overrides any limits set in your run control file.  While
\fBsendmail\fR(8) normally initiates delivery of a message immediately
after receiving the message terminator, some SMTP listeners are not so
prompt.  MTAs like \fIsmail\fR(8) may wait till the
delivery socket is shut down to deliver.  This may produce annoying
delays when \fIfetchmail\fR is processing very large batches.  Setting
the batch limit to some nonzero size will prevent these delays.  This
option does not work with ETRN or ODMR.
.TP
.B \-B <number> | \-\-fetchlimit <number>
(Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a single
poll.  By default there is no limit. An explicit --fetchlimit of 0
overrides any limits set in your run control file.
This option does not work with ETRN or ODMR.
.TP
.B \-\-fetchsizelimit <number>
(Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given server in
a single transaction.  This option is useful in reducing the delay in
downloading the first mail when there are too many mails in the
mailbox.  By default, the limit is 100.  If set to 0, sizes of all
messages are downloaded at the start.
This option does not work with ETRN or ODMR.  For POP3, the only valid
non-zero value is 1.
.TP
.B \-\-fastuidl <number>
(Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID. Binary
search avoids downloading the UIDs of all mails. This saves time
(especially in daemon mode) where downloading the same set of UIDs in
each poll is a waste of bandwidth. The number 'n' indicates how rarely
a linear search should be done. In daemon mode, linear search is used
once followed by binary searches in 'n-1' polls if 'n' is greater than
1; binary search is always used if 'n' is 1; linear search is always
used if 'n' is 0. In non-daemon mode, binary search is used if 'n' is
1; otherwise linear search is used.
This option works with POP3 only.
.TP
.B \-e <count> | \-\-expunge <count>
(keyword: expunge)
Arrange for deletions to be made final after a given number of
messages.  Under POP2 or POP3, fetchmail cannot make deletions final
without sending QUIT and ending the session -- with this option on,
fetchmail will break a long mail retrieval session into multiple
sub-sessions, sending QUIT after each sub-session. This is a good
defense against line drops on POP3 servers that do not do the
equivalent of a QUIT on hangup.  Under IMAP,
.I fetchmail
normally issues an EXPUNGE command after each deletion in order to
force the deletion to be done immediately.  This is safest when your
connection to the server is flaky and expensive, as it avoids
resending duplicate mail after a line hit.  However, on large
mailboxes the overhead of re-indexing after every message can slam the
server pretty hard, so if your connection is reliable it is good to do
expunges less frequently.  Also note that some servers enforce a delay
of a few seconds after each quit, so fetchmail may not be able to get
back in immediately after an expunge -- you may see "lock busy" errors
if this happens. If you specify this option to an integer N,
it tells
.I fetchmail
to only issue expunges on every Nth delete.  An argument of zero
suppresses expunges entirely (so no expunges at all will be done until
the end of run).  This option does not work with ETRN or ODMR.
.SS Authentication Options
.TP
.B \-u <name> | \-\-username <name>
(Keyword: user[name])
Specifies the user identification to be used when logging in to the mailserver.
The appropriate user identification is both server and user-dependent.
The default is your login name on the client machine that is running
.IR fetchmail .
See USER AUTHENTICATION below for a complete description.
.TP
.B \-I <specification> | \-\-interface <specification>
(Keyword: interface)
Require that a specific interface device be up and have a specific local
or remote IPv4 (IPv6 is not supported by this option yet) address (or
range) before polling.  Frequently \fIfetchmail\fP
is used over a transient point-to-point TCP/IP link established directly
to a mailserver via SLIP or PPP.  That is a relatively secure channel.
But when other TCP/IP routes to the mailserver exist (e.g. when the link
is connected to an alternate ISP), your username and password may be
vulnerable to snooping (especially when daemon mode automatically polls
for mail, shipping a clear password over the net at predictable
intervals).  The --interface option may be used to prevent this.  When
the specified link is not up or is not connected to a matching IP
address, polling will be skipped.  The format is:
.sp
.nf
        interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]
.fi
.sp
The field before the first slash is the interface name (i.e. sl0, ppp0
etc.).  The field before the second slash is the acceptable IP address.
The field after the second slash is a mask which specifies a range of
IP addresses to accept.  If no mask is present 255.255.255.255 is
assumed (i.e. an exact match).  This option is currently only supported
under Linux and FreeBSD. Please see the
.B monitor
section for below for FreeBSD specific information.
.sp
Note that this option may be removed from a future fetchmail version.
.TP
.B \-M <interface> | \-\-monitor <interface>
(Keyword: monitor)
Daemon mode can cause transient links which are automatically taken down
after a period of inactivity (e.g. PPP links) to remain up
indefinitely.  This option identifies a system TCP/IP interface to be
monitored for activity.  After each poll interval, if the link is up but
no other activity has occurred on the link, then the poll will be
skipped.  However, when fetchmail is woken up by a signal, the
monitor check is skipped and the poll goes through unconditionally.
This option is currently only supported under Linux and FreeBSD.
For the
.B monitor
and
.B interface
options to work for non root users under FreeBSD, the fetchmail binary
must be installed SGID kmem. This would be a security hole, but
fetchmail runs with the effective GID set to that of the kmem group
.I only
when interface data is being collected.
.sp
Note that this option may be removed from a future fetchmail version.
.TP
.B \-\-auth <type>
(Keyword: auth[enticate])
This option permits you to specify an authentication type (see USER
AUTHENTICATION below for details).  The possible values are \fBany\fR,
\&'\fBpassword\fR', '\fBkerberos_v5\fR' and '\fBkerberos\fR' (or, for
excruciating exactness, '\fBkerberos_v4\fR'), \fRgssapi\fR,
\fIcram-md5\fR, \fIotp\fR, \fIntlm\fR, and \fBssh\fR.  When \fBany\fR (the
default) is specified, fetchmail tries first methods that don't
require a password (GSSAPI, KERBEROS_IV); then it looks for methods
that mask your password (CRAM-MD5, X-OTP, NTLM); and only if the server
doesn't support any of those will it ship your password en clair.
Other values may be used to force various authentication methods
(\fBssh\fR suppresses authentication).  Any value other than
\fIpassword\fR, \fIcram-md5\fR, \fIntlm\fR or \fIotp\fR suppresses fetchmail's
normal inquiry for a password.  Specify \fIssh\fR when you are using
an end-to-end secure connection such as an ssh tunnel; specify
\fRgssapi\fR or \fBkerberos_v4\fR if you are using a protocol variant
that employs GSSAPI or K4.  Choosing KPOP protocol automatically
selects Kerberos authentication.  This option does not work with ETRN.
.SS Miscellaneous Options
.TP
.B \-f <pathname> | \-\-fetchmailrc <pathname>
Specify a non-default name for the
.I ~/.fetchmailrc
run control file.  The pathname argument must be either "-" (a single
dash, meaning to read the configuration from standard input) or a
filename.  Unless the --version option is also on, a named file
argument must have permissions no more open than 0600 (u=rw,g=,o=) or
else be /dev/null.
.TP
.B \-i <pathname> | \-\-idfile <pathname>
(Keyword: idfile)
Specify an alternate name for the .fetchids file used to save POP3
UIDs.
.TP
.B \-n | \-\-norewrite
(Keyword: no rewrite)
Normally,
.I fetchmail
edits RFC-822 address headers (To, From, Cc, Bcc, and Reply-To) in
fetched mail so that any mail IDs local to the server are expanded to
full addresses (@ and the mailserver hostname are appended).  This enables
replies on the client to get addressed correctly (otherwise your
mailer might think they should be addressed to local users on the
client machine!).  This option disables the rewrite.  (This option is
provided to pacify people who are paranoid about having an MTA edit
mail headers and want to know they can prevent it, but it is generally
not a good idea to actually turn off rewrite.)
When using ETRN or ODMR, the rewrite option is ineffective.
.TP
.B \-E <line> | \-\-envelope <line>
(Keyword: envelope; Multidrop only)
This option changes the header
.I fetchmail
assumes will carry a copy of the mail's envelope address.  Normally
this is 'X-Envelope-To' but as this header is not standard, practice
varies. See the discussion of multidrop address handling below.  As a
special case, 'envelope "Received"' enables parsing of sendmail-style
Received lines.  This is the default, and it should not be necessary
unless you have globally disabled Received parsing with 'no envelope'
in the \fI.fetchmailrc\fR file.
.TP
.B \-Q <prefix> | \-\-qvirtual <prefix>
(Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from the user
name found in the header specified with the \fIenvelope\fR option
(\fIbefore\fR doing multidrop name mapping or localdomain checking,
if either is applicable). This option is useful if you are using
.I fetchmail
to collect the mail for an entire domain and your ISP (or your mail
redirection provider) is using qmail.
One of the basic features of qmail is the
.sp
\&'Delivered-To:'
.sp
message header.  Whenever qmail delivers a message to a local mailbox
it puts the username and hostname of the envelope recipient on this
line.  The major reason for this is to prevent mail loops.  To set up
qmail to batch mail for a disconnected site the ISP-mailhost will have
normally put that site in its 'Virtualhosts' control file so it will
add a prefix to all mail addresses for this site. This results in mail
.\" The \&@\& tries to stop HTML converters from making a mailto URL here.
sent to 'username\&@\&userhost.userdom.dom.com' having a
\&'Delivered-To:' line of the form:
.sp
Delivered-To: mbox-userstr-username\&@\&userhost.userdom.dom.com
.sp
The ISP can make the 'mbox-userstr-' prefix anything they choose
but a string matching the user host name is likely.
By using the option 'envelope Delivered-To:' you can make fetchmail reliably
identify the original envelope recipient, but you have to strip the
\&'mbox-userstr-' prefix to deliver to the correct user.
This is what this option is for.
.TP
.B --configdump
Parse the
.I ~/.fetchmailrc
file, interpret any command-line options specified, and dump a
configuration report to standard output.  The configuration report is
a data structure assignment in the language Python.  This option
is meant to be used with an interactive
.I ~/.fetchmailrc
editor like
.IR fetchmailconf ,
written in Python.

.SH USER AUTHENTICATION AND ENCRYPTION
All modes except ETRN require authentication of the client to the server.
Normal user authentication in
.I fetchmail
is very much like the authentication mechanism of
.IR ftp (1).
The correct user-id and password depend upon the underlying security
system at the mailserver.
.PP
If the mailserver is a Unix machine on which you have an ordinary user
account, your regular login name and password are used with
.IR fetchmail .
If you use the same login name on both the server and the client machines,
you needn't worry about specifying a user-id with the
.B \-u
option \-\- the default behavior is to use your login name on the
client machine as the user-id on the server machine.  If you use a
different login name on the server machine, specify that login name
with the
.B \-u
option.  e.g. if your login name is 'jsmith' on a machine named 'mailgrunt',
you would start
.I fetchmail
as follows:
.IP
fetchmail -u jsmith mailgrunt
.PP
The default behavior of
.I fetchmail
is to prompt you for your mailserver password before the connection is
established.  This is the safest way to use
.I fetchmail
and ensures that your password will not be compromised.  You may also specify
your password in your
.I ~/.fetchmailrc
file.  This is convenient when using
.I fetchmail
in daemon mode or with scripts.
.SS Using netrc files
.PP
If you do not specify a password, and
.I fetchmail
cannot extract one from your
.I ~/.fetchmailrc
file, it will look for a
.I ~/.netrc
file in your home directory before requesting one interactively; if an
entry matching the mailserver is found in that file, the password will
be used.  Fetchmail first looks for a match on poll name; if it finds none,
it checks for a match on via name.  See the
.IR ftp (1)
man page for details of the syntax of the
.I ~/.netrc
file.  To show a practical example, a .netrc might look like
this:
.IP
.nf
machine hermes.example.org
login joe
password topsecret
.fi
.PP
You can repeat this block with different user information if you need to
provide more than one password.
.PP
This feature may allow you to avoid duplicating password
information in more than one file.
.PP
On mailservers that do not provide ordinary user accounts, your user-id and
password are usually assigned by the server administrator when you apply for
a mailbox on the server.  Contact your server administrator if you don't know
the correct user-id and password for your mailbox account.
.SS POP3 variants
.PP
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of
independent authentication using the
.I rhosts
file on the mailserver side.  Under this RPOP variant, a fixed
per-user ID equivalent to a password was sent in clear over a link to
a reserved port, with the command RPOP rather than PASS to alert the
server that it should do special checking.  RPOP is supported
by
.I fetchmail
(you can specify 'protocol RPOP' to have the program send 'RPOP'
rather than 'PASS') but its use is strongly discouraged.  This
facility was vulnerable to spoofing and was withdrawn in RFC1460.
.PP
RFC1460 introduced APOP authentication.  In this variant of POP3,
you register an APOP password on your server host (the program
to do this with on the server is probably called \fIpopauth\fR(8)).  You
put the same password in your
.I ~/.fetchmailrc
file.  Each time
.I fetchmail
logs in, it sends a cryptographically secure hash of your password and
the server greeting time to the server, which can verify it by
checking its authorization database.
.SS Alternate authentication forms
.PP
If your \fIfetchmail\fR was built with Kerberos support and you specify
Kerberos authentication (either with --auth or the \fI.fetchmailrc\fR
option \fBauthenticate kerberos_v4\fR) it will try to get a Kerberos
ticket from the mailserver at the start of each query.  Note: if
either the pollname or via name is 'hesiod', fetchmail will try to use
Hesiod to look up the mailserver.
.PP
If you use POP3 or IMAP with GSSAPI authentication, \fIfetchmail\fR will
expect the server to have RFC1731- or RFC1734-conformant GSSAPI
capability, and will use it.  Currently this has only been tested over
Kerberos V, so you're expected to already have a ticket-granting
ticket. You may pass a username different from your principal name
using the standard \fB--user\fR command or by the \fI.fetchmailrc\fR
option \fBuser\fR.
.PP
If your IMAP daemon returns the PREAUTH response in its greeting line,
fetchmail will notice this and skip the normal authentication step.
This can be useful, e.g. if you start imapd explicitly using ssh.
In this case you can declare the authentication value 'ssh' on that
site entry to stop \fI.fetchmail\fR from asking you for a password
when it starts up.
.PP
If you are using POP3, and the server issues a one-time-password
challenge conforming to RFC1938, \fIfetchmail\fR will use your
password as a pass phrase to generate the required response. This
avoids sending secrets over the net unencrypted.
.PP
Compuserve's RPA authentication (similar to APOP) is supported. If you
compile in the support, \fIfetchmail\fR will try to perform an RPA pass-phrase
authentication instead of sending over the password en clair if it
detects "@compuserve.com" in the hostname.
.PP
If you are using IMAP, Microsoft's NTLM authentication (used by Microsoft
Exchange) is supported. If you compile in the support, \fIfetchmail\fR
will try to perform an NTLM authentication (instead of sending over the
password en clair) whenever the server returns AUTH=NTLM in its
capability response. Specify a user option value that looks like
\&'user@domain': the part to the left of the @ will be passed as the
username and the part to the right as the NTLM domain.
.SS Secure Socket Layers (SSL)
.PP
You can access SSL encrypted services by specifying the --ssl option.
You can also do this using the "ssl" server option in the .fetchmailrc
file.  With SSL encryption enabled, queries are initiated over a connection
after negotiating an SSL session.  Some services, such as POP3 and IMAP,
have different well known ports defined for the SSL encrypted services.
The encrypted ports will be selected automatically when SSL is enabled and
no explicit port is specified.
.PP
When connecting to an SSL encrypted server, the server presents a certificate
to the client for validation.  The certificate is checked to verify that
the common name in the certificate matches the name of the server being
contacted and that the effective and expiration dates in the certificate
indicate that it is currently valid.  If any of these checks fail, a warning
message is printed, but the connection continues.  The server certificate
does not need to be signed by any specific Certifying Authority and may
be a "self-signed" certificate.
.PP
Some SSL encrypted servers may request a client side certificate.  A client
side public SSL certificate and private SSL key may be specified.  If
requested by the server, the client certificate is sent to the server for
validation.  Some servers may require a valid client certificate and may
refuse connections if a certificate is not provided or if the certificate
is not valid.  Some servers may require client side certificates be signed
by a recognized Certifying Authority.  The format for the key files and
the certificate files is that required by the underlying SSL libraries
(OpenSSL in the general case).
.PP
A word of care about the use of SSL: While above mentioned
setup with self-signed server certificates retrieved over the wires
can protect you from a passive eavesdropper it doesn't help against an
active attacker. It's clearly an improvement over sending the
passwords in clear but you should be aware that a man-in-the-middle
attack is trivially possible (in particular with tools such as dsniff,
http://www.monkey.org/~dugsong/dsniff/).  Use of an ssh tunnel (see
below for some examples) is preferable if you care seriously about the
security of your mailbox.
.SS SMTP AUTH
.PP
.B fetchmail
also supports authentication to the ESMTP server on the client side
according to RFC 2554.  You can specify a name/password pair to be
used with the keywords 'esmtpname' and 'esmtppassword'; the former
defaults to the username of the calling user.

.SH DAEMON MODE
The
.B \-\-daemon <interval>
or
.B \-d <interval>
option runs
.I fetchmail
in daemon mode.  You must specify a numeric argument which is a
polling interval in seconds.
.PP
In daemon mode,
.I fetchmail
puts itself in background and runs forever, querying each specified
host and then sleeping for the given polling interval.
.PP
Simply invoking
.IP
fetchmail -d 900
.PP
will, therefore, poll all the hosts described in your
.I ~/.fetchmailrc
file (except those explicitly excluded with the 'skip' verb) once
every fifteen minutes.
.PP
It is possible to set a polling interval
in your
.I ~/.fetchmailrc
file by saying 'set daemon <interval>', where <interval> is an
integer number of seconds.  If you do this, fetchmail will always
start in daemon mode unless you override it with the command-line
option --daemon 0 or -d0.
.PP
Only one daemon process is permitted per user; in daemon mode,
.I fetchmail
makes a per-user lockfile to guarantee this.
.PP
Normally, calling fetchmail with a daemon in the background sends a
wake-up signal to the daemon, forcing it to poll mailservers
immediately.  (The wake-up signal is SIGHUP if fetchmail is running as
root, SIGUSR1 otherwise.)  The wake-up action also clears any 'wedged'
flags indicating that connections have wedged due to failed
authentication or multiple timeouts.
.PP
The option
.B --quit
will kill a running daemon process instead of waking it up (if there
is no such process,
.I fetchmail
notifies you).  If the --quit option is the only command-line option,
that's all there is to it.
.PP
The quit option may also be mixed with other command-line options; its
effect is to kill any running daemon before doing what the other
options specify in combination with the fetchmailrc file.
.PP
The
.B \-L <filename>
or
.B \-\-logfile <filename>
option (keyword: set logfile) allows you to redirect status messages
emitted while detached into a specified logfile (follow the
option with the logfile name).  The logfile is opened for append, so
previous messages aren't deleted.  This is primarily useful for
debugging configurations.
.PP
The
.B \-\-syslog
option (keyword: set syslog) allows you to redirect status and error
messages emitted to the
.IR syslog (3)
system daemon if available.
Messages are logged with an id of \fBfetchmail\fR, the facility \fBLOG_MAIL\fR,
and priorities \fBLOG_ERR\fR, \fBLOG_ALERT\fR or \fBLOG_INFO\fR.
This option is intended for logging status and error messages which
indicate the status of the daemon and the results while fetching mail
from the server(s).
Error messages for command line options and parsing the \fI.fetchmailrc\fR
file are still written to stderr, or to the specified log file.
The
.B \-\-nosyslog
option turns off use of
.IR syslog (3),
assuming it's turned on in the
.I ~/.fetchmailrc
file, or that the
.B \-L
or
.B \-\-logfile <file>
option was used.
.PP
The
.B \-N
or --nodetach option suppresses backgrounding and detachment of the
daemon process from its control terminal.  This is useful
for debugging or when fetchmail runs as the child of a supervisor
process such as
.IR init (8)
or Gerrit Pape's
.I runit.
Note that this also causes the logfile option to be
ignored (though perhaps it shouldn't).
.PP
Note that while running in daemon mode polling a POP2 or IMAP2bis server,
transient errors (such as DNS failures or sendmail delivery refusals)
may force the fetchall option on for the duration of the next polling
cycle.  This is a robustness feature.  It means that if a message is
fetched (and thus marked seen by the mailserver) but not delivered
locally due to some transient error, it will be re-fetched during the
next poll cycle.  (The IMAP logic doesn't delete messages until
they're delivered, so this problem does not arise.)
.PP
If you touch or change the
.I ~/.fetchmailrc
file while fetchmail is running in daemon mode, this will be detected
at the beginning of the next poll cycle.  When a changed
.I ~/.fetchmailrc
is detected, fetchmail rereads it and restarts from scratch (using
exec(2); no state information is retained in the new instance).  Note also
that if you break the
.I ~/.fetchmailrc
file's syntax, the new instance will softly and silently vanish away
on startup.

.SH ADMINISTRATIVE OPTIONS
.PP
The
.B \-\-postmaster <name>
option (keyword: set postmaster) specifies the last-resort username to
which multidrop mail is to be forwarded if no matching local recipient
can be found.  Normally this is just the user who invoked
.IR fetchmail .
If the invoking user is root, then the default of this option is
the user 'postmaster'.  Setting postmaster to the empty string causes
such mail to be discarded.
.PP
The
.B \-\-nobounce
option suppresses the normal action of bouncing errors back to the
sender in an RFC1894-conformant error message.  If nobounce is on, the
message will go to the postmaster instead.
.PP
The
.B \-\-invisible
option (keyword: set invisible) tries to make fetchmail invisible.
Normally, fetchmail behaves like any other MTA would -- it generates a
Received header into each message describing its place in the chain of
transmission, and tells the MTA it forwards to that the mail came from
the machine fetchmail itself is running on.  If the invisible option
is on, the Received header is suppressed and fetchmail tries to spoof
the MTA it forwards to into thinking it came directly from the
mailserver host.
.PP
The
.B \-\-showdots
option (keyword: set showdots) forces fetchmail to show progress dots
even if the current tty is not stdout (for example logfiles).
Starting with fetchmail version 5.3.0,
progress dots are only shown on stdout by default.
.PP
By specifying the
.B \-\-tracepolls
option, you can ask fetchmail to add information to the Received
header on the form "polling {label} account {user}", where {label} is
the account label (from the specified rcfile, normally ~/.fetchmailrc)
and {user} is the username which is used to log on to the mail
server. This header can be used to make filtering email where no
useful header information is available and you want mail from
different accounts sorted into different mailboxes (this could, for
example, occur if you have an account on the same server running a
mailing list, and are subscribed to the list using that account). The
default is not adding any such header.  In
.IR .fetchmailrc ,
this is called 'tracepolls'.

.SH RETRIEVAL FAILURE MODES
The protocols \fIfetchmail\fR uses to talk to mailservers are next to
bulletproof.  In normal operation forwarding to port 25, no message is
ever deleted (or even marked for deletion) on the host until the SMTP
listener on the client side has acknowledged to \fIfetchmail\fR that
the message has been either accepted for delivery or rejected due to a
spam block.
.PP
When forwarding to an MDA, however, there is more possibility
of error.  Some MDAs are 'safe' and reliably return a nonzero status
on any delivery error, even one due to temporary resource limits.
The well-known
.IR procmail (1)
program is like this; so are most programs designed as mail transport
agents, such as
.IR sendmail (1),
and
.IR exim (1).
These programs give back a reliable positive acknowledgement and
can be used with the mda option with no risk of mail loss.  Unsafe
MDAs, though, may return 0 even on delivery failure.  If this
happens, you will lose mail.
.PP
The normal mode of \fIfetchmail\fR is to try to download only 'new'
messages, leaving untouched (and undeleted) messages you have already
read directly on the server (or fetched with a previous \fIfetchmail
--keep\fR).  But you may find that messages you've already read on the
server are being fetched (and deleted) even when you don't specify
--all.  There are several reasons this can happen.
.PP
One could be that you're using POP2.  The POP2 protocol includes no
representation of 'new' or 'old' state in messages, so \fIfetchmail\fR
must treat all messages as new all the time.  But POP2 is obsolete, so
this is unlikely.
.PP
A potential POP3 problem might be servers that insert messages
in the middle of mailboxes (some VMS implementations of mail are
rumored to do this).  The \fIfetchmail\fR code assumes that new
messages are appended to the end of the mailbox; when this is not true
it may treat some old messages as new and vice versa.  Using UIDL might
fix this, otherwise, consider switching to IMAP.
.PP
Yet another POP3 problem is that if they can't make tempfiles in the
user's home directory, some POP3 servers will hand back an
undocumented response that causes fetchmail to spuriously report "No
mail".
.PP
The IMAP code uses the presence or absence of the server flag \eSeen
to decide whether or not a message is new.  This isn't the right thing
to do, fetchmail should check the UIDVALIDITY and use UID, but it
doesn't do that yet. Under Unix, it counts on your IMAP server to notice
the BSD-style Status flags set by mail user agents and set the \eSeen
flag from them when appropriate.  All Unix IMAP servers we know of do
this, though it's not specified by the IMAP RFCs.  If you ever trip over
a server that doesn't, the symptom will be that messages you have
already read on your host will look new to the server.  In this
(unlikely) case, only messages you fetched with \fIfetchmail --keep\fR
will be both undeleted and marked old.
.PP
In ETRN and ODMR modes, \fIfetchmail\fR does not actually retrieve messages;
instead, it asks the server's SMTP listener to start a queue flush
to the client via SMTP.  Therefore it sends only undelivered messages.

.SH SPAM FILTERING
Many SMTP listeners allow administrators to set up 'spam filters' that
block unsolicited email from specified domains.  A MAIL FROM or DATA line that
triggers this feature will elicit an SMTP response which
(unfortunately) varies according to the listener.
.PP
Newer versions of
.I sendmail
return an error code of 571.
.PP
According to RFC2821, the correct thing to return in this situation is
550 "Requested action not taken: mailbox unavailable" (the draft adds
"[E.g., mailbox not found, no access, or command rejected for policy
reasons].").
.PP
Older versions of the
.I exim
MTA return 501 "Syntax error in parameters or arguments".
.PP
The
.I postfix
MTA runs 554 as an antispam response.
.PP
.I Zmailer
may reject code with a 500 response (followed by an enhanced status
code that contains more information).
.PP
Return codes which
.I fetchmail
treats as antispam responses and discards
the message can be set with the 'antispam' option.  This is one of the
.I only
three circumstance under which fetchmail ever discards mail (the others
are the 552 and 553 errors described below, and the suppression of
multidropped messages with a message-ID already seen).
.PP
If
.I fetchmail
is fetching from an IMAP server, the antispam response will be detected and
the message rejected immediately after the headers have been fetched,
without reading the message body.  Thus, you won't pay for downloading
spam message bodies.
.PP
By default, the list of antispam responses is empty.
.PP
If the \fIspambounce\fR option is on, mail that is spam-blocked
triggers an RFC1892 bounce message informing the originator that we do
not accept mail from it.

.SH SMTP/ESMTP ERROR HANDLING
Besides the spam-blocking described above, fetchmail takes special
actions on the following SMTP/ESMTP error responses
.TP 5
452 (insufficient system storage)
Leave the message in the server mailbox for later retrieval.
.TP 5
552 (message exceeds fixed maximum message size)
Delete the message from the server.  Send bounce-mail to the
originator.
.TP 5
553 (invalid sending domain)
Delete the message from the server.  Don't even try to send
bounce-mail to the originator.
.PP
Other errors trigger bounce mail back to the originator.

.SH THE RUN CONTROL FILE
The preferred way to set up fetchmail is to write a
\&\fI.fetchmailrc\fR file in your home directory (you may do this
directly, with a text editor, or indirectly via \fIfetchmailconf\fR).
When there is a conflict between the command-line arguments and the
arguments in this file, the command-line arguments take precedence.
.PP
To protect the security of your passwords,
your \fI~/.fetchmailrc\fR may not normally have more than 0600 (u=rw,g=,o=) permissions;
.I fetchmail
will complain and exit otherwise (this check is suppressed when
--version is on).
.PP
You may read the \fI.fetchmailrc\fR file as a list of commands to
be executed when
.I fetchmail
is called with no arguments.
.SS Run Control Syntax
.PP
Comments begin with a '#' and extend through the end of the line.
Otherwise the file consists of a series of server entries or global
option statements in a free-format, token-oriented syntax.
.PP
There are four kinds of tokens: grammar keywords, numbers
(i.e. decimal digit sequences), unquoted strings, and quoted strings.
A quoted string is bounded by double quotes and may contain
whitespace (and quoted digits are treated as a string).  An unquoted
string is any whitespace-delimited token that is neither numeric, string
quoted nor contains the special characters ',', ';', ':', or '='.
.PP
Any amount of whitespace separates tokens in server entries, but is
otherwise ignored. You may use standard C-style escapes (\en, \et,
\eb, octal, and hex) to embed non-printable characters or string
delimiters in strings.
.PP
Each server entry consists of one of the keywords 'poll' or 'skip',
followed by a server name, followed by server options, followed by any
number of user descriptions.  Note: the most common cause of syntax
errors is mixing up user and server options.
.PP
For backward compatibility, the word 'server' is a synonym for 'poll'.
.PP
You can use the noise keywords 'and', 'with',
\&'has', 'wants', and 'options' anywhere in an entry to make
it resemble English.  They're ignored, but but can make entries much
easier to read at a glance.  The punctuation characters ':', ';' and
\&',' are also ignored.
.PP
.SS Poll vs. Skip
The 'poll' verb tells fetchmail to query this host when it is run with
no arguments.  The 'skip' verb tells
.I fetchmail
not to poll this host unless it is explicitly named on the command
line.  (The 'skip' verb allows you to experiment with test entries
safely, or easily disable entries for hosts that are temporarily down.)
.PP
.SS Keyword/Option Summary
Here are the legal options.  Keyword suffixes enclosed in
square brackets are optional.  Those corresponding to command-line
options are followed by '-' and the appropriate option letter.
If option is only relevant to a single mode of operation, it is noted
as 's' or 'm' for singledrop- or multidrop-mode, respectively.

Here are the legal global options:

.TS
l l l lw34.
Keyword         Opt     Mode    Function
_
set daemon      \&      \&      T{
Set a background poll interval in seconds
T}
set postmaster          \&      \&      T{
Give the name of the last-resort mail recipient
T}
set no bouncemail       \&      \&      T{
Direct error mail to postmaster rather than sender
T}
set no spambounce       \&      \&      T{
Send spam bounces
T}
set logfile     \&      \&      T{
Name of a file to dump error and status messages to
T}
set idfile      \&      \&      T{
Name of the file to store UID lists in
T}
set syslog      \&      \&      T{
Do error logging through syslog(3).
T}
set no syslog   \&      \&      T{
Turn off error logging through syslog(3).
T}
set properties  \&      \&      T{
String value is ignored by fetchmail (may be used by extension scripts)
T}
.TE

Here are the legal server options:

.TS
l l l lw34.
Keyword         Opt     Mode    Function
_
via             \&      \&      T{
Specify DNS name of mailserver, overriding poll name
T}
proto[col]      -p      \&      T{
Specify protocol (case insensitive):
POP2, POP3, IMAP, APOP, KPOP
T}
local[domains]  \&      m       T{
Specify domain(s) to be regarded as local
T}
port            -P      \&      T{
Specify TCP/IP service port
T}
auth[enticate]  \&      \&      T{
Set authentication type (default 'any')
T}
timeout         -t      \&      T{
Server inactivity timeout in seconds (default 300)
T}
envelope        -E      m       T{
Specify envelope-address header name
T}
no envelope     \&      m       T{
Disable looking for envelope address
T}
qvirtual        -Q      m       T{
Qmail virtual domain prefix to remove from user name
T}
aka             \&      m       T{
Specify alternate DNS names of mailserver
T}
interface       -I      \&      T{
specify IP interface(s) that must be up for server poll to take place
T}
monitor         -M      \&      T{
Specify IP address to monitor for activity
T}
plugin          \&      \&      T{
Specify command through which to make server connections.
T}
plugout         \&      \&      T{
Specify command through which to make listener connections.
T}
dns             \&      m       T{
Enable DNS lookup for multidrop (default)
T}
no dns          \&      m       T{
Disable DNS lookup for multidrop
T}
checkalias      \&      m       T{
Do comparison by IP address for multidrop
T}
no checkalias   \&      m       T{
Do comparison by name for multidrop (default)
T}
uidl            -U      \&      T{
Force POP3 to use client-side UIDLs
T}
no uidl         \&      \&      T{
Turn off POP3 use of client-side UIDLs (default)
T}
interval        \&      \&      T{
Only check this site every N poll cycles; N is a numeric argument.
T}
tracepolls      \&      \&      T{
Add poll tracing information to the Received header
T}
principal       \&      \&      T{
Set Kerberos principal (only useful with imap and kerberos)
T}
esmtpname       \&      \&      T{
Set name for RFC2554 authentication to the ESMTP server.
T}
esmtppassword           \&      \&      T{
Set password for RFC2554 authentication to the ESMTP server.
T}
.TE

Here are the legal user options:

.TS
l l l lw34.
Keyword         Opt     Mode    Function
_
user[name]      -u      \&      T{
Set remote user name
(local user name if name followed by 'here')
T}
is              \&      \&      T{
Connect local and remote user names
T}
to              \&      \&      T{
Connect local and remote user names
T}
pass[word]      \&      \&      T{
Specify remote account password
T}
ssl             \&      \&      T{
Connect to server over the specified base protocol using SSL encryption
T}
sslcert         \&      \&      T{
Specify file for client side public SSL certificate
T}
sslkey          \&      \&      T{
Specify file for client side private SSL key
T}
sslproto        \&      \&      T{
Force ssl protocol for connection
T}
folder          -r      \&      T{
Specify remote folder to query
T}
smtphost        -S      \&      T{
Specify smtp host(s) to forward to
T}
fetchdomains    \&      m       T{
Specify domains for which mail should be fetched
T}
smtpaddress     -D      \&      T{
Specify the domain to be put in RCPT TO lines
T}
smtpname        \&      \&      T{
Specify the user and domain to be put in RCPT TO lines
T}
antispam        -Z      \&      T{
Specify what SMTP returns are interpreted as spam-policy blocks
T}
mda             -m      \&      T{
Specify MDA for local delivery
T}
bsmtp           -o      \&      T{
Specify BSMTP batch file to append to
T}
preconnect      \&      \&      T{
Command to be executed before each connection
T}
postconnect     \&      \&      T{
Command to be executed after each connection
T}
keep            -k      \&      T{
Don't delete seen messages from server
T}
flush           -F      \&      T{
Flush all seen messages before querying (DANGEROUS)
T}
limitflush      \&      \&      T{
Flush all oversized messages before querying
T}
fetchall        -a      \&      T{
Fetch all messages whether seen or not
T}
rewrite         \&      \&      T{
Rewrite destination addresses for reply (default)
T}
stripcr         \&      \&      T{
Strip carriage returns from ends of lines
T}
forcecr         \&      \&      T{
Force carriage returns at ends of lines
T}
pass8bits       \&      \&      T{
Force BODY=8BITMIME to ESMTP listener
T}
dropstatus      \&      \&      T{
Strip Status and X-Mozilla-Status lines out of incoming mail
T}
dropdelivered   \&      \&      T{
Strip Delivered-To lines out of incoming mail
T}
mimedecode      \&      \&      T{
Convert quoted-printable to 8-bit in MIME messages
T}
idle            \&      \&      T{
Idle waiting for new messages after each poll (IMAP only)
T}
no keep         -K      \&      T{
Delete seen messages from server (default)
T}
no flush        \&      \&      T{
Don't flush all seen messages before querying (default)
T}
no fetchall     \&      \&      T{
Retrieve only new messages (default)
T}
no rewrite      \&      \&      T{
Don't rewrite headers
T}
no stripcr      \&      \&      T{
Don't strip carriage returns (default)
T}
no forcecr      \&      \&      T{
Don't force carriage returns at EOL (default)
T}
no pass8bits    \&      \&      T{
Don't force BODY=8BITMIME to ESMTP listener (default)
T}
no dropstatus   \&      \&      T{
Don't drop Status headers (default)
T}
no dropdelivered        \&      \&      T{
Don't drop Delivered-To headers (default)
T}
no mimedecode   \&      \&      T{
Don't convert quoted-printable to 8-bit in MIME messages (default)
T}
no idle         \&      \&      T{
Don't idle waiting for new messages after each poll (IMAP only)
T}
limit           -l      \&      T{
Set message size limit
T}
warnings        -w      \&      T{
Set message size warning interval
T}
batchlimit      -b      \&      T{
Max # messages to forward in single connect
T}
fetchlimit      -B      \&      T{
Max # messages to fetch in single connect
T}
fetchsizelimit  \&      \&      T{
Max # message sizes to fetch in single transaction
T}
fastuidl        \&      \&      T{
Use binary search for first unseen message (POP3 only)
T}
expunge         -e      \&      T{
Perform an expunge on every #th message (IMAP and POP3 only)
T}
properties      \&      \&      T{
String value is ignored by fetchmail (may be used by extension scripts)
T}
.TE
.PP
Remember that all user options must \fIfollow\fR all server options.
.PP
In the .fetchmailrc file, the 'envelope' string argument may be
preceded by a whitespace-separated number.  This number, if specified,
is the number of such headers to skip (that is, an argument of 1
selects the second header of the given type).  This is sometime useful
for ignoring bogus Received headers created by an ISP's local delivery
agent.
.SS Keywords Not Corresponding To Option Switches
.PP
The 'folder' and 'smtphost' options (unlike their command-line
equivalents) can take a space- or comma-separated list of names
following them.
.PP
All options correspond to the obvious command-line arguments, except
the following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns',
\&'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect',
\&'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr',
\&'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus',
\&'dropdelivered/no dropdelivered', 'mimedecode/no mimedecode', 'idle/no
idle', and 'no envelope'.
.PP
The 'via' option is for if you want to have more
than one configuration pointing at the same site.  If it is present,
the string argument will be taken as the actual DNS name of the
mailserver host to query.
This will override the argument of poll, which can then simply be a
distinct label for the configuration (e.g. what you would give on the
command line to explicitly query this host).
.PP
The 'interval' option (which takes a numeric argument) allows you to poll a
server less frequently than the basic poll interval.  If you say
\&'interval N' the server this option is attached to will only be
queried every N poll intervals.
.PP
The 'is' or 'to' keywords associate the following local (client)
name(s) (or server-name to client-name mappings separated by =) with
the mailserver user name in the entry.  If an is/to list has '*' as
its last name, unrecognized names are simply passed through.
.PP
A single local name can be used to support redirecting your mail when
your username on the client machine is different from your name on the
mailserver.  When there is only a single local name, mail is forwarded
to that local username regardless of the message's Received, To, Cc,
and Bcc headers.  In this case
.I fetchmail
never does DNS lookups.
.PP
When there is more than one local name (or name mapping) the
\fIfetchmail\fR code does look at the Received, To, Cc, and Bcc
headers of retrieved mail (this is 'multidrop mode').  It looks for
addresses with hostname parts that match your poll name or your 'via',
\&'aka' or 'localdomains' options, and usually also for hostname parts
which DNS tells it are aliases of the mailserver.  See the discussion
of 'dns', 'checkalias', 'localdomains', and 'aka' for details on how
matching addresses are handled.
.PP
If \fIfetchmail\fR cannot match any mailserver usernames or
localdomain addresses, the mail will be bounced.
Normally it will be bounced to the sender, but if 'nobounce' is on
it will go to the postmaster (which in turn defaults to being the
calling user).
.PP
The 'dns' option (normally on) controls the way addresses from
multidrop mailboxes are checked.  On, it enables logic to check each
host address that doesn't match an 'aka' or 'localdomains' declaration
by looking it up with DNS.  When a mailserver username is recognized
attached to a matching hostname part, its local mapping is added to
the list of local recipients.
.PP
The 'checkalias' option (normally off) extends the lookups performed
by the 'dns' keyword in multidrop mode, providing a way to cope with
remote MTAs that identify themselves using their canonical name, while
they're polled using an alias.
When such a server is polled, checks to extract the envelope address
fail, and
.IR fetchmail
reverts to delivery using the To/Cc/Bcc headers (See below
\&'Header vs. Envelope addresses').
Specifying this option instructs
.IR fetchmail
to retrieve all the IP addresses associated with both the poll name
and the name used by the remote MTA and to do a comparison of the IP
addresses.  This comes in handy in situations where the remote server
undergoes frequent canonical name changes, that would otherwise
require modifications to the rcfile.  'checkalias' has no effect if
\&'no dns' is specified in the rcfile.
.PP
The 'aka' option is for use with multidrop mailboxes.  It allows you
to pre-declare a list of DNS aliases for a server.  This is an
optimization hack that allows you to trade space for speed.  When
.IR fetchmail ,
while processing a multidrop mailbox, grovels through message headers
looking for names of the mailserver, pre-declaring common ones can
save it from having to do DNS lookups.  Note: the names you give
as arguments to 'aka' are matched as suffixes -- if you specify
(say) 'aka netaxs.com', this will match not just a hostname
netaxs.com, but any hostname that ends with '.netaxs.com'; such as
(say) pop3.netaxs.com and mail.netaxs.com.
.PP
The 'localdomains' option allows you to declare a list of domains
which fetchmail should consider local.  When fetchmail is parsing
address lines in multidrop modes, and a trailing segment of a host
name matches a declared local domain, that address is passed through
to the listener or MDA unaltered (local-name mappings are \fInot\fR
applied).
.PP
If you are using 'localdomains', you may also need to specify \&'no
envelope', which disables \fIfetchmail\fR's normal attempt to deduce
an envelope address from the Received line or X-Envelope-To header or
whatever header has been previously set by 'envelope'.  If you set 'no
envelope' in the defaults entry it is possible to undo that in
individual entries by using 'envelope <string>'.  As a special case,
\&'envelope "Received"' restores the default parsing of
Received lines.
.PP
The \fBpassword\fR option requires a string argument, which is the password
to be used with the entry's server.
.PP
The 'preconnect' keyword allows you to specify a shell command to be
executed just before each time
.I fetchmail
establishes a mailserver connection.  This may be useful if you are
attempting to set up secure POP connections with the aid of
.IR ssh (1).
If the command returns a nonzero status, the poll of that mailserver
will be aborted.
.PP
Similarly, the 'postconnect' keyword similarly allows you to specify a
shell command to be executed just after each time a mailserver
connection is taken down.
.PP
The 'forcecr' option controls whether lines terminated by LF only are
given CRLF termination before forwarding.  Strictly speaking RFC821
requires this, but few MTAs enforce the requirement it so this option
is normally off (only one such MTA, qmail, is in significant use at
time of writing).
.PP
The 'stripcr' option controls whether carriage returns are stripped
out of retrieved mail before it is forwarded.  It is normally not
necessary to set this, because it defaults to 'on' (CR stripping
enabled) when there is an MDA declared but 'off' (CR stripping
disabled) when forwarding is via SMTP.  If 'stripcr' and 'forcecr' are
both on, 'stripcr' will override.
.PP
The 'pass8bits' option exists to cope with Microsoft mail programs that
stupidly slap a "Content-Transfer-Encoding: 7bit" on everything.  With
this option off (the default) and such a header present,
.I fetchmail
declares BODY=7BIT to an ESMTP-capable listener; this causes problems for
messages actually using 8-bit ISO or KOI-8 character sets, which will
be garbled by having the high bits of all characters stripped.  If
\&'pass8bits' is on,
.I fetchmail
is forced to declare BODY=8BITMIME to any ESMTP-capable listener.  If
the listener is 8-bit-clean (as all the major ones now are) the right
thing will probably result.
.PP
The 'dropstatus' option controls whether nonempty Status and
X-Mozilla-Status lines are retained in fetched mail (the default) or
discarded.  Retaining them allows your MUA to see what messages (if
any) were marked seen on the server.  On the other hand, it can
confuse some new-mail notifiers, which assume that anything with a
Status line in it has been seen.  (Note: the empty Status lines
inserted by some buggy POP servers are unconditionally discarded.)
.PP
The 'dropdelivered' option controls whether Delivered-To headers will
be kept in fetched mail (the default) or discarded. These headers are
added by Qmail and Postfix mailservers in order to avoid mail loops but
may get in your way if you try to "mirror" a mailserver within the same
domain. Use with caution.
.PP
The 'mimedecode' option controls whether MIME messages using the
quoted-printable encoding are automatically converted into pure 8-bit
data. If you are delivering mail to an ESMTP-capable, 8-bit-clean
listener (that includes all of the major MTAs like sendmail), then
this will automatically convert quoted-printable message headers and
data into 8-bit data, making it easier to understand when reading
mail. If your e-mail programs know how to deal with MIME messages,
then this option is not needed.  The mimedecode option is off by
default, because doing RFC2047 conversion on headers throws away
character-set information and can lead to bad results if the encoding
of the headers differs from the body encoding.
.PP
The 'idle' option is intended to be used with IMAP servers supporting
the RFC2177 IDLE command extension, but does not strictly require it.
If it is enabled, and fetchmail detects that IDLE is supported, an
IDLE will be issued at the end of each poll.  This will tell the IMAP
server to hold the connection open and notify the client when new mail
is available.  If IDLE is not supported, fetchmail will simulate it by
periodically issuing NOOP. If you need to poll a link frequently, IDLE
can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT
sequences. On the other hand, an IDLE connection will eat almost all
of your fetchmail's time, because it will never drop the connection
and allow other pools to occur unless the server times out the IDLE.
It also doesn't work with multiple folders; only the first folder will
ever be polled.

.PP
The 'properties' option is an extension mechanism.  It takes a string
argument, which is ignored by fetchmail itself.  The string argument may be
used to store configuration information for scripts which require it.
In particular, the output of '--configdump' option will make properties
associated with a user entry readily available to a Python script.
.PP
.SS Miscellaneous Run Control Options
The words 'here' and 'there' have useful English-like
significance.  Normally 'user eric is esr' would mean that
mail for the remote user 'eric' is to be delivered to 'esr',
but you can make this clearer by saying 'user eric there is esr here',
or reverse it by saying 'user esr here is eric there'
.PP
Legal protocol identifiers for use with the 'protocol' keyword are:
.sp
.nf
    auto (or AUTO)
    pop2 (or POP2)
    pop3 (or POP3)
    sdps (or SDPS)
    imap (or IMAP)
    apop (or APOP)
    kpop (or KPOP)
.fi
.sp
.PP
Legal authentication types are 'any', 'password', 'kerberos', 'kerberos_v5'
and 'gssapi', 'cram-md5', 'otp', 'ntlm', 'ssh'.
The 'password' type specifies authentication by normal transmission of a
password (the password may be plain text or subject to
protocol-specific encryption as in APOP); 'kerberos' tells
\fIfetchmail\fR to try to get a Kerberos ticket at the start of each
query instead, and send an arbitrary string as the password; and
\&'gssapi' tells fetchmail to use GSSAPI authentication.  See the description
of the 'auth' keyword for more.
.PP
Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4
authentication.  These defaults may be overridden by later options.
.PP
There are currently four global option statements; 'set logfile'
followed by a string sets the same global specified by --logfile.  A
command-line --logfile option will override this.  Also, 'set daemon'
sets the poll interval as --daemon does.  This can be overridden by a
command-line --daemon option; in particular --daemon 0 can be used to
force foreground operation. The 'set postmaster' statement sets the
address to which multidrop mail defaults if there are no local
matches.  Finally, 'set syslog' sends log messages to syslogd(8).

.SH INTERACTION WITH RFC 822
When trying to determine the originating address of a message,
fetchmail looks through headers in the following order:
.sp
.nf
        Return-Path:
        Resent-Sender: (ignored if it doesn't contain an @ or !)
        Sender: (ignored if it doesn't contain an @ or !)
        Resent-From:
        From:
        Reply-To:
        Apparently-From:
.fi
.sp
The originating address is used for logging, and to set the MAIL FROM
address when forwarding to SMTP.  This order is intended to cope
gracefully with receiving mailing list messages in multidrop mode. The
intent is that if a local address doesn't exist, the bounce message
won't be returned blindly to the author or to the list itself, but
rather to the list manager (which is less annoying).

In multidrop mode, destination headers are processed as follows:
First, fetchmail looks for the Received: header (or whichever one is
specified by the 'envelope' option) to determine the local
recipient address. If the mail is addressed to more than one recipient,
the Received line won't contain any information regarding recipient addresses.

Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc:
lines.  If they exist, they should contain the final recipients and
have precedence over their To:/Cc:/Bcc: counterparts.  If the Resent-*
lines don't exist, the To:, Cc:, Bcc: and Apparently-To: lines are
looked for. (The presence of a Resent-To: is taken to imply that the
person referred by the To: address has already received the original
copy of the mail.)

.SH CONFIGURATION EXAMPLES
Note that although there are password declarations in a good many
of the examples below, this is mainly for illustrative purposes.
We recommend stashing account/password pairs in your $HOME/.netrc
file, where they can be used not just by fetchmail but by ftp(1) and
other programs.

Basic format is:

.nf
  poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD
.fi
.PP
Example:

.nf
  poll pop.provider.net protocol pop3 username "jsmith" password "secret1"
.fi
.PP
Or, using some abbreviations:

.nf
  poll pop.provider.net proto pop3 user "jsmith" password "secret1"
.fi
.PP
Multiple servers may be listed:

.nf
  poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
  poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"
.fi

Here's a version of those two with more whitespace and some noise words:

.nf
  poll pop.provider.net proto pop3
      user "jsmith", with password secret1, is "jsmith" here;
  poll other.provider.net proto pop2:
      user "John.Smith", with password "My^Hat", is "John.Smith" here;
.fi

This version is much easier to read and doesn't cost significantly
more (parsing is done only once, at startup time).

.PP
If you need to include whitespace in a parameter string, enclose the
string in double quotes.  Thus:

.nf
  poll mail.provider.net with proto pop3:
        user "jsmith" there has password "u can't krak this"
                    is jws here and wants mda "/bin/mail"
.fi

You may have an initial server description headed by the keyword
\&'defaults' instead of 'poll' followed by a name.  Such a record
is interpreted as defaults for all queries to use. It may be overwritten
by individual server descriptions.  So, you could write:

.nf
  defaults proto pop3
        user "jsmith"
  poll pop.provider.net
        pass "secret1"
  poll mail.provider.net
        user "jjsmith" there has password "secret2"
.fi

It's possible to specify more than one user per server (this is only
likely to be useful when running fetchmail in daemon mode as root).
The 'user' keyword leads off a user description, and every user specification
in a multi-user entry must include it.  Here's an example:

.nf
  poll pop.provider.net proto pop3 port 3111
        user "jsmith" with pass "secret1" is "smith" here
        user jones with pass "secret2" is "jjones" here keep
.fi

This associates the local username 'smith' with the pop.provider.net
username 'jsmith' and the local username 'jjones' with the
pop.provider.net username 'jones'.  Mail for 'jones' is kept on the
server after download.
.PP
Here's what a simple retrieval configuration for a multi-drop mailbox
looks like:

.nf
  poll pop.provider.net:
        user maildrop with pass secret1 to golux 'hurkle'='happy' snark here
.fi

This says that the mailbox of account 'maildrop' on the server is a
multi-drop box, and that messages in it should be parsed for the
server user names 'golux', 'hurkle', and 'snark'.  It further
specifies that 'golux' and 'snark' have the same name on the
client as on the server, but mail for server user 'hurkle' should be
delivered to client user 'happy'.
.PP
Here's an example of another kind of multidrop connection:

.nf
  poll pop.provider.net localdomains loonytoons.org toons.org:
        user maildrop with pass secret1 to * here
.fi

This also says that the mailbox of account 'maildrop' on the server is
a multi-drop box.  It tells fetchmail that any address in the
loonytoons.org or toons.org domains (including sub-domain addresses like
\&'joe@daffy.loonytoons.org') should be passed through to the local SMTP
listener without modification.  Be careful of mail loops if you do this!
.PP
Here's an example configuration using ssh and the plugin option.  The
queries are made directly on the stdin and stdout of imapd via ssh.
Note that in this setup, IMAP authentication can be skipped.

.nf
poll mailhost.net with proto imap:
        plugin "ssh %h /usr/sbin/imapd" auth ssh;
        user esr is esr here
.fi

.SH THE USE AND ABUSE OF MULTIDROP MAILBOXES
Use the multiple-local-recipients feature with caution -- it can bite.
All multidrop features are ineffective in ETRN and ODMR modes.

Also, note that in multidrop mode duplicate mails are suppressed.  A
piece of mail is considered duplicate if it has the same message-ID as
the message immediately preceding and more than one addressee.  Such
runs of messages may be generated when copies of a message addressed
to multiple users are delivered to a multidrop box.

.SS Header vs. Envelope addresses
The fundamental problem is that by having your mailserver toss several
peoples' mail in a single maildrop box, you may have thrown away
potentially vital information about who each piece of mail was
actually addressed to (the 'envelope address', as opposed to the
header addresses in the RFC822 To/Cc/Bcc headers).  This 'envelope
address' is the address you need in order to reroute mail properly.
.PP
Sometimes
.I fetchmail
can deduce the envelope address.  If the mailserver MTA is
.I sendmail
and the item of mail had just one recipient, the MTA will have written
a 'by/for' clause that gives the envelope addressee into its Received
header. But this doesn't work reliably for other MTAs, nor if there is
more than one recipient.  By default, \fIfetchmail\fR looks for
envelope addresses in these lines; you can restore this default with
-E "Received" or \&'envelope Received'.
.PP
Alternatively, some SMTP listeners and/or mail servers insert a header
in each message containing a copy of the envelope addresses.  This
header (when it exists) is often 'X-Envelope-To'.  Fetchmail's
assumption about this can be changed with the -E or 'envelope' option.
Note that writing an envelope header of this kind exposes the names of
recipients (including blind-copy recipients) to all receivers of the
messages; it is therefore regarded by some administrators as a
security/privacy problem.
.PP
A slight variation of the 'X-Envelope-To' header is the 'Delivered-To' put
by qmail to avoid mail loops. It will probably prefix the user name with a
string that normally matches the user's domain. To remove this prefix you
can use the -Q or 'qvirtual' option.
.PP
Sometimes, unfortunately, neither of these methods works.  When they
all fail, fetchmail must fall back on the contents of To/Cc/Bcc
headers to try to determine recipient addressees -- and these are not
reliable.  In particular, mailing-list software often ships mail with
only the list broadcast address in the To header.
.PP
When
.I fetchmail
cannot deduce a recipient address that is local, and the intended
recipient address was anyone other than fetchmail's invoking user,
mail will get lost.  This is what makes the multidrop feature risky.
.PP
A related problem is that when you blind-copy a mail message, the Bcc
information is carried \fIonly\fR as envelope address (it's not put
in the headers fetchmail can see unless there is an X-Envelope
header).  Thus, blind-copying to someone who gets mail over a
fetchmail link will fail unless the the mailserver host routinely
writes X-Envelope or an equivalent header into messages in your maildrop.

.SS Good Ways To Use Multidrop Mailboxes
Multiple local names can be used to administer a mailing list from the
client side of a \fIfetchmail\fR collection.  Suppose your name is
\&'esr', and you want to both pick up your own mail and maintain a mailing
list called (say) "fetchmail-friends", and you want to keep the alias
list on your client machine.
.PP
On your server, you can alias \&'fetchmail-friends' to 'esr'; then, in
your \fI.fetchmailrc\fR, declare \&'to esr fetchmail-friends here'.
Then, when mail including 'fetchmail-friends' as a local address
gets fetched, the list name will be appended to the list of
recipients your SMTP listener sees.  Therefore it will undergo alias
expansion locally.  Be sure to include 'esr' in the local alias
expansion of fetchmail-friends, or you'll never see mail sent only to
the list.  Also be sure that your listener has the "me-too" option set
(sendmail's -oXm command-line option or OXm declaration) so your name
isn't removed from alias expansions in messages you send.
.PP
This trick is not without its problems, however.  You'll begin to see
this when a message comes in that is addressed only to a mailing list
you do \fInot\fR have declared as a local name.  Each such message
will feature an 'X-Fetchmail-Warning' header which is generated
because fetchmail cannot find a valid local name in the recipient
addresses.  Such messages default (as was described above) to being
sent to the local user running
.IR fetchmail ,
but the program has no way to know that that's actually the right thing.

.SS Bad Ways To Abuse Multidrop Mailboxes
Multidrop mailboxes and
.I fetchmail
serving multiple users in daemon mode do not mix.  The problem, again, is
mail from mailing lists, which typically does not have an individual
recipient address on it.   Unless
.I fetchmail
can deduce an envelope address, such mail will only go to the account
running fetchmail (probably root).  Also, blind-copied users are very
likely never to see their mail at all.
.PP
If you're tempted to use
.I fetchmail
to retrieve mail for multiple users from a single mail drop via POP or
IMAP, think again (and reread the section on header and envelope
addresses above).  It would be smarter to just let the mail sit in the
mailserver's queue and use fetchmail's ETRN or ODMR modes to trigger
SMTP sends periodically (of course, this means you have to poll more
frequently than the mailserver's expiry period).  If you can't arrange
this, try setting up a UUCP feed.
.PP
If you absolutely \fImust\fR use multidrop for this purpose, make sure
your mailserver writes an envelope-address header that fetchmail can
see.  Otherwise you \fIwill\fR lose mail and it \fIwill\fR come back
to haunt you.

.SS Speeding Up Multidrop Checking
Normally, when multiple users are declared
.I fetchmail
extracts recipient addresses as described above and checks each host
part with DNS to see if it's an alias of the mailserver.  If so, the
name mappings described in the "to ... here" declaration are done and
the mail locally delivered.
.PP
This is a convenient but also slow method.  To speed
it up, pre-declare mailserver aliases with 'aka'; these are checked
before DNS lookups are done.  If you're certain your aka list contains
.B all
DNS aliases of the mailserver (and all MX names pointing at it - note
this may change in a future version)
you can declare 'no dns' to suppress DNS lookups entirely and
\fIonly\fR match against the aka list.

.SH EXIT CODES
To facilitate the use of
.I fetchmail
in shell scripts, an exit code is returned to give an indication
of what occurred during a given connection.
.PP
The exit codes returned by
.I fetchmail
are as follows:
.IP 0
One or more messages were successfully retrieved (or, if the -c option
was selected, were found waiting but not retrieved).
.IP 1
There was no mail awaiting retrieval.  (There may have been old mail still
on the server but not selected for retrieval.)
.IP 2
An error was encountered when attempting to open a socket to retrieve
mail.  If you don't know what a socket is, don't worry about it --
just treat this as an 'unrecoverable error'.  This error can also be
because a protocol fetchmail wants to use is not listed in /etc/services.
.IP 3
The user authentication step failed.  This usually means that a bad
user-id, password, or APOP id was specified.  Or it may mean that you
tried to run fetchmail under circumstances where it did not have
standard input attached to a terminal and could not prompt for a
missing password.
.IP 4
Some sort of fatal protocol error was detected.
.IP 5
There was a syntax error in the arguments to
.IR fetchmail .
.IP 6
The run control file had bad permissions.
.IP 7
There was an error condition reported by the server.  Can also
fire if
.I fetchmail
timed out while waiting for the server.
.IP 8
Client-side exclusion error.  This means
.I fetchmail
either found another copy of itself already running, or failed in such
a way that it isn't sure whether another copy is running.
.IP 9
The user authentication step failed because the server responded "lock
busy".  Try again after a brief pause!  This error is not implemented
for all protocols, nor for all servers.  If not implemented for your
server, "3" will be returned instead, see above.  May be returned when
talking to qpopper or other servers that can respond with "lock busy"
or some similar text containing the word "lock".
.IP 10
The
.I fetchmail
run failed while trying to do an SMTP port open or transaction.
.IP 11
Fatal DNS error.  Fetchmail encountered an error while performing
a DNS lookup at startup and could not proceed.
.IP 12
BSMTP batch file could not be opened.
.IP 13
Poll terminated by a fetch limit (see the --fetchlimit option).
.IP 14
Server busy indication.
.IP 15
Server timed out during an IMAP IDLE.
.IP 23
Internal error.  You should see a message on standard error with
details.
.PP
When
.I fetchmail
queries more than one host, return status is 0 if \fIany\fR query
successfully retrieved mail. Otherwise the returned error status is
that of the last host queried.

.SH FILES
.TP 5
~/.fetchmailrc
default run control file
.TP 5
~/.fetchids
default location of file associating hosts with last message IDs seen
(used only with newer RFC1939-compliant POP3 servers supporting the
UIDL command).
.TP 5
~/.fetchmail.pid
lock file to help prevent concurrent runs (non-root mode).
.TP 5
~/.netrc
your FTP run control file, which (if present) will be searched for
passwords as a last resort before prompting for one interactively.
.TP 5
/var/run/fetchmail.pid
lock file to help prevent concurrent runs (root mode, Linux systems).
.TP 5
/etc/fetchmail.pid
lock file to help prevent concurrent runs (root mode, systems without /var/run).

.SH ENVIRONMENT
If the FETCHMAILUSER variable is set, it is used as the name of the
calling user (default local name) for purposes such as mailing error
notifications.  Otherwise, if either the LOGNAME or USER variable is
correctly set (e.g. the corresponding UID matches the session user ID)
then that name is used as the default local name.  Otherwise
\fBgetpwuid\fR(3) must be able to retrieve a password entry for the
session ID (this elaborate logic is designed to handle the case of
multiple names per userid gracefully).

If the environment variable FETCHMAILHOME is set to a valid and
existing directory name, the .fetchmailrc and .fetchids and
\&.fetchmail.pid files are put there instead of in the invoking user's
home directory (and lose the leading dots on their names).  The
\&.netrc file is looked for in the the invoking user's home directory
regardless of FETCHMAILHOME's setting.

If the HOME_ETC variable is set, file $HOME_ETC/.fetchmailrc is used
instead of ~/.fetchmailrc.

.SH SIGNALS
If a
.I fetchmail
daemon is running as root, SIGHUP wakes it up from its sleep phase and
forces a poll of all non-skipped servers (this is in accordance with
the usual conventions for system daemons).
.PP
If
.I fetchmail
is running in daemon mode as non-root, use SIGUSR1 to wake it (this is
so SIGHUP due to logout can retain the default action of killing it).
.PP
Running
.I fetchmail
in foreground while a background fetchmail is running will do
whichever of these is appropriate to wake it up.

.SH BUGS AND KNOWN PROBLEMS
.PP
The assumptions that the DNS and in particular the checkalias options
make are not often sustainable. For instance, it has become uncommon for
an MX server to be a POP3 or IMAP server at the same time. Therefore the
MX lookups may go away in a future release.
.PP
The mda and plugin options interact badly.  In order to collect error
status from the MDA, fetchmail has to change its normal signal
handling so that dead plugin processes don't get reaped until the end
of the poll cycle.  This can cause resource starvation if too many
zombies accumulate.  So either don't deliver to a MDA using plugins or
risk being overrun by an army of undead.
.PP
The --interface option does not support IPv6 and it is doubtful if it
ever will, since there is no portable way to query interface IPv6
addresses.
.PP
The RFC822 address parser used in multidrop mode chokes on some
@-addresses that are technically legal but bizarre.  Strange uses of
quoting and embedded comments are likely to confuse it.
.PP
In a message with multiple envelope headers, only the last one
processed will be visible to fetchmail.  To get around this, use a
mailserver-side filter that consolidates the contents of all envelope
headers into a single one (procmail, mailagent, or maildrop can be
programmed to do this fairly easily).
.PP
Use of some of these protocols requires that the program send
unencrypted passwords over the TCP/IP connection to the mailserver.
This creates a risk that name/password pairs might be snaffled with a
packet sniffer or more sophisticated monitoring software.  Under Linux
and FreeBSD, the --interface option can be used to restrict polling to
availability of a specific interface device with a specific local or
remote IP address, but snooping is still possible if (a) either host
has a network device that can be opened in promiscuous mode, or (b)
the intervening network link can be tapped.  We recommend the use of
.IR ssh (1)
tunnelling to not only shroud your passwords but encrypt the entire
conversation.
.PP
Use of the %F or %T escapes in an mda option could open a security
hole, because they pass text manipulable by an attacker to a shell
command.  Potential shell characters are replaced by '_' before
execution.  The hole is further reduced by the fact that fetchmail
temporarily discards any suid privileges it may have while running the
MDA.  For maximum safety, however, don't use an mda command containing
%F or %T when fetchmail is run from the root account itself.
.PP
Fetchmail's method of sending bouncemail and spam bounces requires that
port 25 of localhost be available for sending mail via SMTP.
.PP
If you modify a
.I ~/.fetchmailrc
while a background instance is running and break the syntax, the
background instance will die silently.  Unfortunately, it can't
die noisily because we don't yet know whether syslog should be enabled.
On some systems, fetchmail dies quietly even if there is no syntax
error; this seems to have something to do with buggy terminal ioctl
code in the kernel.
.PP
The -f - option (reading a configuration from stdin) is incompatible
with the plugin option.
.PP
The 'principal' option only handles Kerberos IV, not V.
.PP
Send comments, bug reports, gripes, and the like to the
fetchmail-devel list <fetchmail-devel@lists.berlios.de>.  An HTML FAQ is
available at the fetchmail home page; surf to
http://fetchmail.berlios.de/ or do a WWW search for pages with
\&'fetchmail' in their titles.

.SH AUTHOR
Eric S. Raymond <esr@snark.thyrsus.com>.  Too many other people to
name here have contributed code and patches.
This program is descended from and replaces
.IR popclient ,
by Carl Harris <ceharris@mal.com>; the internals have become quite different,
but some of its interface design is directly traceable to that
ancestral program.
.PP
This manual page has been improved by R.\ Hannes Beinert.
.PP
Fetchmail is currently maintained by Matthias Andree and Rob Funk.

.SH SEE ALSO
mutt(1), elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5)
.SH APPLICABLE STANDARDS
.TP 5
SMTP/ESMTP:
RFC 821, RFC2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985,
RFC 2554.
.TP 5
mail:
RFC 822, RFC2822, RFC 1123, RFC 1892, RFC 1894.
.TP 5
POP2:
RFC 937
.TP 5
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC1734, RFC 1939, RFC 1957,
RFC2195, RFC 2449.
.TP 5
APOP:
RFC 1460, RFC 1725, RFC 1939.
.TP 5
RPOP:
RFC 1081, RFC 1225.
.TP 5
IMAP2/IMAP2BIS:
RFC 1176, RFC 1732.
.TP 5
IMAP4/IMAP4rev1:
RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177,
RFC 2683.
.TP 5
ETRN:
RFC 1985.
.TP 5
ODMR/ATRN:
RFC 2645.
.TP 5
OTP:
RFC 1938.
.TP 5
LMTP:
RFC 2033.
.TP 5
GSSAPI:
RFC 1508.
.TP 5
TLS:
RFC 2595.