How to not use "localhost.localdomain" in outgoing HELO/EHLO?

Question

I've tried just about everything I could and I can't get "localhost" to get out of my email headers. I ended up on the CBL list at Spamhaus, so I'm trying to fix this before I apply to get delisted.

I have setup DKIM, SPF, Sender-ID auth. The problem is PHP or NGINX is passing the email to Postfix from localhost.

I get these "Received:" headers inserted on outgoing mail:

Received: from mydomain.com (unknown [127.0.0.1]) by mail.mydomain.com (Postfix) with ESMTP id 452762A068
Received: (from nginx@localhost) by mydomain.com (8.14.4/8.14.4/Submit) id r9THAQAP002693;

I think I need to clear up the unknown and 127.0.0.1, as well as the localhost with the nginx username. I'm running CentOS 6.3. Thanks in advance for your help.

Answer 1

CBL "localhost.localdomain" listing

Your host had been listed for name "localhost.localdomain" it had send out in helo/ehlo command.

You can fix name used in outgoing helo/ehlo command using one of the following:

• changing hostname as reported by hostname --fqdn
  (FQDN = Fully Qualified Domain Name)
  It may be OS/distribution dependent. It fixes similar problems in most MTAs.

• smtp_helo_name option in postfix configuration

Quote from the CBL page:

This IP address is HELO'ing as "localhost.localdomain" which violates the relevant standards (specifically: RFC5321).
The CBL does not list for RFC violations per-se. This particular behaviour, however, correlates strongly to spambot infections. In other words, out of thousands upon thousands of IP addresses HELO'ing this way, all but a handful are infected and spewing junk.