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293946Re: myhostname and PTR

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  • Noel Jones
    Jun 21, 2013
      On 6/21/2013 10:24 AM, Titanus Eramius wrote:
      > Hello
      > I've searched several times about information on the PTR record, and
      > what myhostname in main.cf should be. The problem is not the
      > information, but the fact that I struggle to understand it...

      Ideally, the PTR, A record, and HELO hostname should all agree.

      > This server runs with the IP address from a hosted VPS, and
      > using dig to do a reverse lookup gives
      > 46-21-105-38-static.serverhotell.net.

      There doesn't appear to be a matching A record for that PTR, so the
      setup is incomplete. Postfix will label such a host as "unknown".
      Most sites (but not all!) will still accept your mail.

      Best to request your hosting company to give you a custom PTR with
      your domain name, something like smtp.example.com, mx1.example.com,
      mail.example.com, etc. so your server looks like a mail server and
      not a random infected bot. If this host handles several domains,
      just pick one for the PTR and A record. No need to list them all.

      Whatever PTR you end up with, there should be a matching A record
      with the server address.

      > Does this means I should use 46-21-105-38-static as myhostname?

      While technically correct to use the
      46-21-105-38-static.serverhotell.net hostname, that's the same name
      a random infected bot will use and should be avoided.

      I would still suggest a myhostname setting that makes you look like
      a mail server instead of a random bot, even if it doesn't match the
      PTR. Make sure you also have an A record set for the hostname that
      points back to your server's IP.

      -- Noel Jones
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