Our organization will be implementing a clustered Barracuda solution, in front of Zimbra. We want to only allow SMTP traffic for our organization to route through the Barracuda boxes, but allow SMTP Auth from anywhere in the world.
The standard way to configure this, would be to place the Zimbra mail server behind our firewall, and allow SMTP traffic, only from the Barracuda box. However, if we do this, we will also be blocking users from using Zimbra for SMTP Auth.
Is there a way to assign a different port for SMTP traffic (this would be blocked, except from the Barracuda boxes), and only allow SMTP Auth on port 25?