diff -rup /tmp/fetchmail-6.3.21//daemon.c ./daemon.c
--- /tmp/fetchmail-6.3.21//daemon.c	2011-08-21 15:34:58.000000000 +0200
+++ ./daemon.c	2012-02-19 21:10:16.200367846 +0100
@@ -53,9 +53,7 @@
 #include "fetchmail.h"
 #include "tunable.h"
 
-static RETSIGTYPE
-sigchld_handler (int sig)
-/* process SIGCHLD to obtain the exit code of the terminating process */
+int wait_for_child(pid_t who)
 {
 #if 	defined(HAVE_WAITPID)				/* the POSIX way */
     int status;
@@ -70,13 +68,23 @@ sigchld_handler (int sig)
     int status;
 #endif
 
-    while ((pid = wait3(&status, WNOHANG, 0)) > 0)
+    while ((pid = wait4(who, &status, WNOHANG, 0)) > 0)
 	continue; /* swallow 'em up. */
 #else	/* Zooks! Nothing to do but wait(), and hope we don't block... */
     int status;
 
     wait(&status);
 #endif
+
+    return (int)status;
+}
+
+static RETSIGTYPE
+sigchld_handler (int sig)
+/* process SIGCHLD to obtain the exit code of the terminating process */
+{
+    wait_for_child(-1);
+
     lastsig = SIGCHLD;
     (void)sig;
 }
diff -rup /tmp/fetchmail-6.3.21//fetchmail.c ./fetchmail.c
--- /tmp/fetchmail-6.3.21//fetchmail.c	2011-08-21 15:34:58.000000000 +0200
+++ ./fetchmail.c	2012-02-19 21:13:05.279377301 +0100
@@ -1393,11 +1393,24 @@ static RETSIGTYPE terminate_poll(int sig
 #endif /* POP3_ENABLE */
 }
 
+extern pid_t mda_pid;
+
 static RETSIGTYPE terminate_run(int sig)
 /* to be executed on normal or signal-induced termination */
 {
     struct query	*ctl;
 
+    /* 
+     * kill explicitly the MDA process so that it dies *before* fetchmail
+	 * otherwise an uncomplete message might be delivered generating garbage
+	 * in the maildir/mailbox
+     */
+    if( (sig == SIGINT || sig == SIGTERM ) && mda_pid != 0)
+    {
+      report(stdout, GT_("killing MDA with PID %d\n"), mda_pid);
+      kill(mda_pid, sig);
+    }
+
     terminate_poll(sig);
 
     /* 
diff -rup /tmp/fetchmail-6.3.21//sink.c ./sink.c
--- /tmp/fetchmail-6.3.21//sink.c	2012-02-19 17:57:37.000000000 +0100
+++ ./sink.c	2012-02-19 21:11:07.518370716 +0100
@@ -632,6 +632,7 @@ static int handle_smtp_report_without_bo
 
 /* these are shared by open_sink and stuffline */
 static FILE *sinkfp;
+pid_t mda_pid = 0;
 
 int stuffline(struct query *ctl, char *buf)
 /* ship a line to the given control block's output sink (SMTP server or MDA) */
@@ -1102,6 +1103,7 @@ static int open_mda_sink(struct query *c
     struct	idlist *idp;
     int	length = 0, fromlen = 0, nameslen = 0;
     char	*names = NULL, *before, *after, *from = NULL;
+    int mda_pipe[2];
 
     (void)bad_addresses;
     xfree(ctl->destaddr);
@@ -1219,7 +1221,7 @@ static int open_mda_sink(struct query *c
 
 
     if (outlevel >= O_DEBUG)
-	report(stdout, GT_("about to deliver with: %s\n"), before);
+	report(stdout, GT_("about to deliver with: '%s'\n"), before);
 
 #ifdef HAVE_SETEUID
     /*
@@ -1235,7 +1237,29 @@ static int open_mda_sink(struct query *c
     }
 #endif /* HAVE_SETEUID */
 
-    sinkfp = popen(before, "w");
+    if(pipe(mda_pipe) != 0) {
+	report(stderr, GT_("Cannot create a pipe for the MDA: %s\n"), strerror(errno));
+	return PS_IOERR;
+    }
+
+	/* save client's (MDA) PID in a global var for a clean shutdown in the fetchmail signal handler */
+    mda_pid = fork();
+    if(mda_pid < 0) {
+	report(stderr, GT_("Unable to fork for the MDA dispatching: %s\n"), strerror(errno));
+	return PS_IOERR;
+    }
+	else if(mda_pid == 0) { /* child */
+	/* close the write-end of the pipe connecting the stdin of the mda process to the read-end */
+	close(mda_pipe[1]);
+	dup2(mda_pipe[0], STDIN_FILENO);
+
+	execl("/bin/sh", "sh", "-c", before, NULL);
+	report(stderr, GT_("Unable to exec the MDA: %s\n"), strerror(errno));
+	return PS_IOERR;
+    }
+
+    close(mda_pipe[0]);
+    sinkfp = fdopen(mda_pipe[1], "w");
     free(before);
     before = NULL;
 
@@ -1249,6 +1273,7 @@ static int open_mda_sink(struct query *c
 
     if (!sinkfp)
     {
+	mda_pid = 0;
 	report(stderr, GT_("MDA open failed\n"));
 	return(PS_IOERR);
     }
@@ -1338,8 +1363,10 @@ void release_sink(struct query *ctl)
     {
 	if (sinkfp)
 	{
-	    pclose(sinkfp);
+	    fclose(sinkfp); // send EOF to the pipe
 	    sinkfp = (FILE *)NULL;
+		wait_for_child(mda_pid);
+		mda_pid = 0;
 	}
 	deal_with_sigchld(); /* Restore SIGCHLD handling to reap zombies */
     }
@@ -1381,11 +1408,12 @@ int close_sink(struct query *ctl, struct
 	{
 	    if (ferror(sinkfp))
 		err = 1, e2 = errno;
-	    if ((fflush(sinkfp)))
+	    if (fclose(sinkfp)) // send EOF to the pipe
 		err = 1, e2 = errno;
 
 	    errno = 0;
-	    rc = pclose(sinkfp);
+		rc = wait_for_child(mda_pid);
+		mda_pid = 0;
 	    e = errno;
 	    sinkfp = (FILE *)NULL;
 	}
@@ -1404,8 +1432,8 @@ int close_sink(struct query *ctl, struct
 			GT_("MDA returned nonzero status %d\n"), WEXITSTATUS(rc));
 	    } else {
 		report(stderr,
-			GT_("Strange: MDA pclose returned %d and errno %d/%s, cannot handle at %s:%d\n"),
-			rc, e, strerror(e), __FILE__, __LINE__);
+			GT_("Unexpected error %d/%s waiting for MDA process, cannot handle at %s:%d\n"),
+			e, strerror(e), __FILE__, __LINE__);
 	    }
 
 	    return(FALSE);