URGENT!! How to block SMTP port from public address?

RouterOS General
1

Hi, this is my problem… I’m using a MT 2.9.27 router for share ADSL connection with 5 pc (intranet). Someone use my public IP like a SMTP server for spamming action. How I can stop this? I think I need to block traffic on port 25 on public ethernet card, but how I can make this?

Thank You

Paolo

2

Take a look here

http://wiki.mikrotik.com/wiki/Firewall

Regards

Andrew