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I'm running Postfix on a RHEL7 server. I've started to use a new iPhone to send email, and I'm seeing this in mail.log:

Oct 30 20:15:56 kyushu2 postfix/smtpd[31145]: warning: hostname ue.tmodns.net does not resolve to address 172.58.200.63
Oct 30 20:15:56 kyushu2 postfix/smtpd[31145]: connect from unknown[172.58.200.63]
Oct 30 20:15:56 kyushu2 postfix/smtpd[31145]: NOQUEUE: reject: RCPT from unknown[172.58.200.63]: 454 4.7.1 <xxx@kxxx.com>: Relay access denied; from=<tim@timboyer.org> to=<xxx@xxx.com> proto=ESMTP helo=<smtpclient.apple>

My assumption is that Postfix sees me as trying to use timboyer.org as an open relay. I don't particularly want to allow all iPhone users to use my mail server as a relay. Is there a way to allow just @timboyer.org to relay?

Thanks,

Tim

Paul
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Tim Boyer
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    Don't. It is only a matter of time until you have spammers trying to use your open relay to send email that seem to originate from your domain. Fix the real issue which is that you should authenticate, and relay should be allowed after authentication. – NiKiZe Oct 31 '21 at 01:19
  • Please post the output of `postconf -n`. – Paul Oct 31 '21 at 13:29

1 Answers1

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NiKiZe, your answer is absolutely correct. I spent Sunday reading and was going to come back on with a 'never mind!' - I'm working on implementing SASL right now.

http://www.postfix.org/SASL_README.html#testing_saslauthd

Thanks very much for the pointer, and yeah, some spammer would have figured out the open relay thing eventually. :)

Tim Boyer
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