Thanks Klug! Now I found that I had a different config in Server settings and Global settings.
Server settings are correct from my point of view (no DNS lookups, relay MTA as IP address.
In the Global settings there is no relay MTA specified and DNS lookups are enabled.
zmprov gcf zimbraMtaDnsLookupsEnabled returns TRUE.
In the Global settings there is said that "Server settings override global settings" - now I do not know if this is really true !?
Anyway - after I changed the settings on the Global tab, the problem still persists. zimbraMtaDnsLookupsEnabled now returns FALSE. It looks like Zimbra does some re-recursion, as it is possible that it asks local DNS for the FQDN of the IP address of relay MTA and then it again asks local DNS for the IP of previously learned FQDN, but that way it will get the internal IP of the Exchange instead of the external one that is explicitly set - above DNS are just guesses. Without host entry for the Exchange external IP it just does not work as expected.  |