Hey, first of all thanks the Zimbra staff for developing a great product.

Second I'm new to Zimbra and Linux in general (Mostly ussing MS servers all my life) but with the help of this forum and the Zimbra docs I was able to migrate our old 4.5 Zimbra to the new mail server with Ver 5.

Now everything is working as expected the only problem I have is that my outside trusted networks clients (Clients accessing via Internet) wich are using Mail Clients (ie. Outlook, etc) are not able to send emails to external domains (aka error 554 <xxx@xxx.xxx>: Relay access denied).

I know this isn't a Zimbra bug/error and I'm sure I'm missing one more configuration option/command.

Here are my MTA Configuration right now:

Enable authentication is checked
TLS authentication only is checked

MTA trusted networks: 200.87.XXX.XXX
(200.87.XXX.XXX is the external IP for the mail server, the other networks were changed for security but are reflecting the same idea)

Enable Dns lookups is checked

I tried some of the suggestions in these forums about enable "smtp Authentication for my outgoing server" on my outlook test client but as soon I enable that it cannot connect to the server anymore, I think thats related to explicit reject rule wich I cannot find, but I do not know if that will solve my problem.

I already read hxxp://wiki.zimbra.com/index.php?title=ZimbraMtaMyNetworks wiki wich doesnt help me on this cause the clients will be connecting from IP addresses wich are not known to me.

I will appreciate any help you can give me and thanks in advance.