Iredmail does not send mail to SOME addresses, what could be the problem?

Question

Mail server

Iredmail does not send mail to SOME addresses, what could be the problem?
An excerpt from the log looks like this:

418981008A7: host mx01.ggo.ru[194.150.178.25] said: 450 4.7.1 Client host rejected: cannot find your hostname, [x.x.171.46] (in reply to RCPT TO command)
Apr 10 10:34:49 mail postfix/smtp[28728]: 418981008A7: to=<[email protected]>, relay=smtp.ggo.ru[178.209.107.21]:25, delay=21, delays=0.09/0.03/21/0.13, dsn=4.0.0, status=deferred (host smtp.ggo.ru[178.209.107.21] said: 450 Client host rejected: cannot find your hostname, [x.x.171.46] (in reply to RCPT TO command))

Tell me, how can I fix this miracle? =)

Answer 1

You don't have a writeback on the server. Write it down and there will be chocolate. In general, this is the first thing to do on mail servers.