How to fix sending messages in Zimbra?

Question

postfix

I can't send a message to a couple of domains, the
logs give an error:
Jan 6 15:27:19 mail postfix/smtp[21565]: B17C381505: to=, relay=webmail.dom.ru[80.100.100.100]:25, delay=4763, delays=4761/0.1/1.5/0.07, dsn=4.7.1, status=deferred (host webmail.dom.ru[80.100.100.100] said: 450 4.7.1 Client host rejected: cannot find your hostname, [10.10.103.53 ] (in reply to RCPT TO command))
PTR record is 53.103.10.10.in-addr.arpa IN PTR mail.mydomane.com
The letter is hanging in the message queue and that's it ((
tell me where to dig, thanks!

Answer 1

You answered your own question. You need a valid ptr entry pointing to the hostname from which the mail is being sent.