Linux Mail Server Setup and Howto Guide

If your Postfix mail server has multiple IP addresses, it will use the same SMTP hostname greeting on every IP Address. This may cause a problem since some mail servers check the SMTP hostname banner to see if the hostname points to the same mail server. If not, any mail you send may be rejected or handled as spam. You can confirm if you have this problem by getting a DNS report on your domain name.

Sample DNS report, the hostnames are not real. Note that it shows the same SMTP banner 220 mail.acme.local ESMTP Postfix from the two hostnames, mail.acme.local and mail2.acme.local.

1. Edit the file /etc/postfix/master.cf and change the line below from

smtp inet n - n - - smtpd

to this

localhost:smtp  inet n - n - - smtpd
ipaddress1:smtp inet n - n - - smtpd
ipaddress2:smtp inet n - n - - smtpd -o myhostname=hostname2
.
.
.
ipaddressn:smtp inet n - n - - smtpd -o myhostname=hostnamen

The new settings above binds each ip address to a new hostname except for localhost and ipaddress1 which uses the regular hostname.

2. Restart the Postfix service or the MailScanner service if you have integrated MailScanner into Postfix.

3. Check your DNS report again, you should now pass the Mailserver greeting test.

Visit the forum to ask for help or to give a comment.

***
Posted on 12/29/2007 and last updated on 11/7/2009
Filed under Postfix

        

 

4 Responses to “Postfix Multiple IP Address, Individual SMTP Hostname Greeting”

1. harsh:
   October 14th, 2008 at 11:33 pm

   configure all redhat linux server by
   command(samba,apache,sendmail,nis,
   dhcp etc….)

2. mouss:
   February 9th, 2009 at 9:26 pm

   you seem to believe that an “outgoing” relay is also an “inbound” server (MX). most large organisations have different servers for these.

   anyway, there is no sane filter that will connect back to the smtp “client” (which may not accept connections if it is an MSA) and check its banner.

   and no sane filter would connect to the MX of the sender address to do that either. try comparing the “outgoing” relays of google, yahoo, … any ISP, and their MXes.

   if you have evidence, please show it, so that we hit on the silly filter author or admins!

3. consultant:
   February 9th, 2009 at 11:04 pm

   Hi mouss,

   I checked google and yahoo and both failed on the mail server greeting test which means it is not necessary. I reconfigured my mail server just to pass on that test. The config is not much of a hassle so I did it anyway.

4. Postfix Multiple IP Address, Individual SMTP Hostname Greeting — Trials & Tribulations:
   September 11th, 2009 at 2:39 am

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