I'm having a problem with some of the emails coming into our Zimbra Server.
Under Global Settings -> MTA
SMTP error from remote mail server after RCPT TO:<firstname.lastname@example.org>:
host mail.domain.com [xxx.xxx.xxx.xxx]: 450 4.7.1 Client host rejected:
cannot find your hostname, [220.127.116.11]: retry timeout exceeded
I have for Protocol Checks:
(Checked) Hostname in greeting violates RFC (reject_invalid_hostname)
(Not Checked) Client must greet with a fully qualified hostname (reject_non_fqdn_hostname)
(Checked) Sender address must be fully qualified (reject_non_fqdn_sender)
Now, problem is, if I were to do a reverse IP lookup for 18.104.22.168 I get
(Checked) Client's IP address (reject_unknown_client)
(Unchecked) Hostname in greeting (reject_unknown_hostname)
(Checked) Sender's domain (reject_unknown_sender_domain)
a valid DNS name back (This is done via nslookup being run on the Zimbra machine).
What am I missing here in order to get these bounces to stop happening?