HELP - reverse dns and email pbm - SOLVED

Moriah · Last edited by Moriah on Sun Jul 29, 2018 11:50 am; edited 1 time in total

I recently switched network connectivity providers, with a consequence that my ip address changed. I had my DNS entries changed for my web server and my email server, but the reverse DNS was not changed; therefore, my domain name resolves to the correct ip address, but that ip address does not resolve back to my domain name, it resolves to the cable privider's name.

I am having trouble with my sendmail mail server in that many people are unable to receive my emails. I can receive theirs ok. I can receive email that I send to myself, but that stays on my local network. My sendmail configuration has not changed since everything worked on the old ip address.

Is the reverse DNS likely the problem with others being unable to receive my emails?
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szatox · Advocate Joined: 27 Aug 2013 Posts: 3133

It is a very common check and many email servers do indeed reject emails from "wrong" domains, where MTA's advertised name does not match PTR.
Also, use DKIM. Telling the receiving server you're not a random bot is a good start, even if you never had a chance to build your reputation.

bunder · Bodhisattva Joined: 10 Apr 2004 Posts: 5934

Yes, your A has to have a PTR and they have to match.
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Ant P. · Watchman Joined: 18 Apr 2009 Posts: 6920

Do you have a SPF record for the mail server? Adding that might help even if the PTR can't be fixed.

Moriah · Posted: Sun Jul 01, 2018 2:08 pm Post subject:

@Ant P.
I am not running the DNS, and I am pretty ignorant about the email specific DNS records. Does the SPF record go in the name server, or the mail server? If it is something I can fix by editing my /etc/sendmail.mc file, that would make it easy.
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The MyWord KJV Bible tool is at http://www.elilabs.com/~myword

Foghorn Leghorn is a Warner Bros. cartoon character.

szatox · Advocate Joined: 27 Aug 2013 Posts: 3133

SPF is a TXT record for bare domain.
DKIM is also a TXT record in _<selector>._domainkey.your.domain.

You can't set them if you don't control DNS

Ant P. · Watchman Joined: 18 Apr 2009 Posts: 6920

A simple SPF record would look like this (in `dig`):

Moriah · Posted: Sun Jul 01, 2018 9:38 pm Post subject:

I will speak with the DNS administrator tomorrow. Thanks!

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The MyWord KJV Bible tool is at http://www.elilabs.com/~myword

Foghorn Leghorn is a Warner Bros. cartoon character.

Moriah · Posted: Sun Jul 29, 2018 11:50 am Post subject:

The problem has been solved.
_________________
The MyWord KJV Bible tool is at http://www.elilabs.com/~myword

Foghorn Leghorn is a Warner Bros. cartoon character.