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I sent myself an e-mail from my server to my gmail account, here is one of the headers (partially redacted):

Received: from cpvds3xx.xxx.com (dev1.xxx.com. [209.51.132.xxx])
        by mx.google.com with ESMTPS id b71si12090017yhf.148.2014.03.06.12.09.35
        for <xxx@gmail.com>
        (version=TLSv1 cipher=RC4-SHA bits=128/128);
        Thu, 06 Mar 2014 12:09:35 -0800 (PST)

I would like to know where does cpvds3xx.xxx.com come from. I understand that it is a host name, but what is the source of that information? Does exim send it? Does it come from my DNS zone file? rDNS entry? or is there something else?

Background: cpvds3xx.xxx.com is a host name of a virtual server, and dev1.xxx.com is one of the web sites hosted on that server. WHM + cPanel + exim + LAMP

And a more practical question, how do I align that name with the name of my web site (dev1.xxx.com)?

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  • "Background: cpvsds3xx.xxx.com is a"... a what? – ETL Mar 06 '14 at 21:21
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    Baseline SMTP knowledge (so voting to close) - the line is inserted by the SMTP Server. Every server has to do so, it is part of the SMTP specs. WHere the line comes from is something not specified - google has to be asked. As in: it is the responsibility of the server to determine the dns behind the IP. – TomTom Mar 06 '14 at 21:26
  • See [RFC 2821](http://tools.ietf.org/html/rfc2821). – Mike Lowery Mar 07 '14 at 02:57

1 Answers1

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Received: from NAME-USED-IN-HELO-COMMAND (REVERSE-DNS [IP-ADDRESS]) ...

  1. NAME-USED-IN-HELO-COMMAND - name used by the sending host as its name in EHLO/HELO command in the SMTP session
  2. REVERSE-DNS - name provided by PTR record in closed PTR-A loop
    IP-ADDRESS -> "PTR" -> DNS-NAME -> "A" -> IP-ADDRESS

See RFC-5321 4.4 Trace Information for more information

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  • Make sense. My `/etc/hostname` (#1 in your list) is `cpvds3xx`, and rDNS is `dev1.xxx.com` (#2 in your list). – THX-1138 Mar 07 '14 at 14:53