Setup Zimbra Collaboration Suite on a cloud server without public interface (read: behind NAT) may waste you an afternoon trying to figure out why local emails (same domain) are not delivered, while sending/receiving mail from/to the internet works flawless.
You may find something like this on your
May 7 04:32:39 mail postfix/lmtp: connect to mail.mydomain.com[XXX.XXX.XXX.XXX]:25: Connection timed out
XXX.XXX.XXX.XXX is the public ip address of your zimbra server.
Problem is that Zimbra MTA performs DNS lookups for local mail delivery by default. Check your Zimbra configuration and you will find out the trick:```
su - zimbra zmlocalconfig | grep postfix_lmtp_host_lookup postfix_lmtp_host_lookup = dns
Now, let’s fix it:
su - zimbra zmlocalconfig -e postfix_lmtp_host_lookup=native
then restart the MTA:
Note that you MUST flag
Enable DNS lookups under
Server settings / MTA or outgoing mail will stop to work.