Originally Posted by skot999
I'm not quite there yet because I can't explain why the HELO greet string is totally different when telnetting to the outside IP.
If you don't mind sending me the private IP, I would propose trying to do a manual smtp transaction by running the following commands from one of our zimbra servers (you could do this yourself too, you just need to do it from a mail server with proper public DNS records):
Sorry to be stubborn on this one point!
telnet your_outside_IP 25
mail from: <email@example.com>
rcpt to: <your_email_address@your_zimbra_domain>
Testing, 1, 2, 3
All the best,