Question : Block SMTP service

Hi guys,

we have a Netgear FVS318v3 router and in the Rules menu there is an entry in Outbound Services which looks like this:

Service Name: SMTP
Action: BLOCK always
Lan Users: 192.168.1.3 - 192.168.1.254
Wan Users: Any      
Log: Match

We also have one more office that connects to us through VPN. We have a Netgear FVS318v2 there. What I noticed is that SMTP isn't blocked in Outbound Services there. Do you think it's a good idea to block it there or will it prevent users from other office from being able to send emails? Or can I just add one more rule in our main router that would say:

Service Name: SMTP
Action: BLOCK always
Lan Users: 192.168.0.1 - 192.168.0.254 (this is our VPN IPs)
Wan Users: Any      
Log: Match

Answer : Block SMTP service

I recommend that port 25 is blocked for all outbound traffic except your email server.

By blocking port 25 you can quickly spot a compromised machine on your network that is sending out spam.

If you aren't running your own email server then that isn't practical.

Simon.