I am running Zentyal 3.2 on a different machine (I've been running it since 3.0) and I seem to remember that the Firewall had services for mail predefined. No longer it seems?
I set up a new test box running 3.5. It is set as standalone (only one internal NIC). My gateway is doing 1-to-1 NAT which makes the Zentyal accessible to the outside world.
When the Firewall is up, I can't receive any email. When I turn the Firewall off, I get email.
I already tried creating a Network service called "Mail" which consists of ACCEPT ANY for TCP on ports 25, 465, and 587. I then added that service to both "Filtering rules for External Networks to Zentyal" and "Filtering rules for Internal Networks to Zentyal". Saved changes. Still doesn't seem to work. What am I missing?