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Currently Exim4 is sending from example.com, but as I understand it is better (for spam ratings?) to send from a subdomain like mail.example.com. How do I make it so that the headers of my emails show it coming from mail.example.com?

Sorry, it must be a very simple answer, but I can't figure it out and searching doesn't seem to bring anything (another sign it is a simple answer).

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I have no knowledge of it being better to send from a mail subdomain. It is better to send from a machine that is validated by a SPF record. –  84104 Aug 8 '11 at 2:52
    
Thanks, I read it here: systemajik.com/blog/detecting-email-server-forgery "A legitimate email server has ... a static addresss with a DNS PTR record specifying the host’s FQDN (Fully Qualified Domain Name). This should have at least three domain components: hostname, sub-domain, and the TLD (top level domain). For example mail.example.com instead of example.com." –  yuttadhammo Aug 8 '11 at 3:24

1 Answer 1

Now that I understand what your asking.

Your (or your ISP's, depending upon your situation) DNS should have these entries for your outbound MTA:
mail.yourdomain.tld IN A 192.0.2.19
19.2.0.192.in-addr.arpa IN PTR mail.yourdomain.tld

This has nothing to do with the domain the email is coming from.

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Thanks for clarifying that... do I need the A entry if I already have a wildcard subdomain entry set (*.example.tld)? –  yuttadhammo Aug 8 '11 at 5:19
    
And I don't understand how this affects outgoing email... do I need to have a separate IP for my mail server then? Sorry for being dense. –  yuttadhammo Aug 8 '11 at 5:22

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