Send e-mails from local Postfix to local Exim on same host

Written by Claudio Kuenzler - 0 comments

Published on October 25th 2012 - Listed in Linux Internet Mail

Today I had to figure out, how an Atmail server, which uses Exim as mail server process, can accept local e-mails, e.g. sent through mailx.
Postfix is also installed on the same machine and Postfix is called from the system. But even when I configured Postfix to use the local ip and the exim port, the mail was rejected by exim with the following error:

Oct 25 12:49:46 atmail postfix/smtp[5513]: CD2CF41791: to=, relay=192.168.23.23[192.168.23.23]:25, delay=0.11, delays=0.01/0/0.03/0.07, dsn=5.0.0, status=bounced (host 192.168.23.23[192.168.23.23] said: 550-Verification failed for 550-Unrouteable address 550 Sender verify failed (in reply to RCPT TO command))

The problem is, that Atmail/exim checks if the sender address exists in the atmail database and/or if the sender address is valid. But as I'm on the same server I don't really care about verification and just want exim to accept the mail.

After a lot of try'n'err I finally got it working with the following configuration.

1. Set up Postfix as "local mailserver" besides Atmail/Exim but let it run under a different port.
Port 25 is already in use by Atmail/Exim, therefore the listening port needs to be changed in /etc/postfix/master.cf:

#smtp      inet  n       -       n       -       -       smtpd # was
2525      inet  n       -       n       -       -       smtpd

In the very first (not commented-out) line is the standard listening definition. By default Postfix should listen on the smtp port, which is 25. But in this case I replaced smtp by "2525".

2. Make some Postfix modifications.
If not already done, set the correct hostname (fqdn) in Postfix's configuration (main.cf):

myhostname = mymailserver.example.com

Also set the relayhost to the same IP-address as this server (localhost or 127.0.0.1 won't work) with port 25 (= Exim):

relayhost = 192.168.23.23:25

Then start Postfix and verify the listening ports:

[root@mymailserver]# /etc/init.d/postfix start

[root@mymailserver]# netstat -lntp | grep 25
tcp        0      0 0.0.0.0:25                  0.0.0.0:*    LISTEN      5081/exim          
tcp        0      0 127.0.0.1:2525              0.0.0.0:*    LISTEN      5711/master

3. Edit the Exim configuration file.
Add a line which defines the server's IP address in the acl_check_rcpt part but, very important, BEFORE the # part.

acl_check_rcpt:

  # Accept if the source is local SMTP (i.e. not over TCP/IP). We do this by
  # testing for an empty sending host field.

  accept  hosts = :
 
  accept  hosts = 192.168.23.23

[...]

#
# Deny unless the sender address can be verified.
require verify = sender
#

In the case of Atmail, this Exim configure file is found in /usr/local/atmail/mailserver/configure.
After this, restart the Exim process:

pkill -HUP exim

4. Send a local e-mail and check logs.

[root@mymailserver]# echo "This is a testmail from Postfix to Exim on same server" | mailx -s "Mailserver-Talk" user@example.com

[root@mymailserver]# tail /var/log/mail.log
Oct 25 13:22:48 mymailserver postfix/pickup[5713]: 91D5241791: uid=0 from=
Oct 25 13:22:48 mymailserver postfix/cleanup[5757]: 91D5241791: message-id=<20121025132248.91D5241791@mymailserver.example.com>
Oct 25 13:22:48 mymailserver postfix/qmgr[5714]: 91D5241791: from=, size=513, nrcpt=1 (queue active)
Oct 25 13:22:49 mymailserver postfix/smtp[5759]: 91D5241791: to=, relay=192.168.23.23[192.168.23.23]:25, delay=0.46, delays=0.04/0.01/0.03/0.39, dsn=2.0.0, status=sent (250 OK id=1TRNOa-0001Uu-L8)
Oct 25 13:22:49 mymailserver postfix/qmgr[5714]: 91D5241791: removed

[root@mymailserver]# tail /usr/local/atmail/mailserver/spool/log/mainlog
2012-10-25 13:22:49 1TRNOa-0001Uu-L8 <= root@mymailserver.example.com H=mymailserver.example.com (mymailserver.example.com) [192.168.23.23] P=esmtp S=1448 id=20121025132248.91D5241791@mymailserver.example.com
2012-10-25 13:22:49 1TRNOa-0001Uu-L8 => user R=mysql_user T=mysql_delivery
2012-10-25 13:22:49 1TRNOa-0001Uu-L8 Completed

Maybe there's a simpler or better solution to that, but as I'm not at all an Exim dude, I'm already happy that it works. If you do have a better solution, please comment.

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