Issue block OUTGOING connections to port 25 except mailserver

[Martin AndrésZ]

Hello, I´m facing an issue with some users that have installed applications like phpmailer, that kind of applications can send mails/spam without pass through the mailserver, for the previous reason I have tryed to add an ougoing restriction to port 25, except for the mail server. I´ve created two rules, one to allow outgoing connections for mailenable smtp binary (MESMTPC.exe) and other to block any traffic to a remote port 25. When I enable the blocking rule then nothing can establish new connections not even the mailserver.

I wonder if any of you have been facing the same issue and if can give me a hand in order to help me solve this.

M