We have an Exchange 2000 server with SP2.
We are currently blocking all ports except:
TCP port 25
TCP port 53
TCP port 80
TCP port 110
TCP port 135
TCP port 1494
TCP port 1723
UDP port 53
UDP port 135
And we are allowing all ICMP traffic to come in.
The problem is that when we apply this access list on the router, we
can't send any SMTP messages out from the server and the queue becomes
full. We can receive messages , but we cannot send messages. Are we
missing any ports that should be allowed through?