Zimbra not sending Some messages

[sigtrap]

Thanks for the quick answer, but after searching a lot I dared to change some settings, and now it works.
(and I found out that my logs didn't work so I set that up too)

I couldn't, sometimes, send emails from the web client. I got following errors:

Web client error:
"message not sent one or more addresses were not accepted" "rejected addresses"

zimbra.log:

postfix/lmtp[29287]: C08D813A1A6C: to=<mail@test.dom>, relay=none, delay=21, delays=0.16/0.04/21/0, dsn=4.4.1, status=deferred (connect to master.test.dom[123.123.123.123]:7025: Connection timed out)

I have a NAT network with only one server.

So obviously lmtp tries to connect to my internet IP and not my NAT IP on port 7075.

I tried lot of different settings and DNS setups and then I saw a screenshot of the Admin GUI in another forum thread.

Under Server->MTA the setting for "Web mail MTA Hostname" should be localhost, and not my domain name!

Now it works.

Thanks for all the help on the forum!
Regards
//Sigtrap