Firewall and SMTP

I need to secure my network. I would like to prevent SMTP from leaving
my network unless it comes from one specified server( email server).
This should prevent my network from becoming a zombie of spams. How to
I go about this? Will protocol binding do ? How do I test if it works?


thanks

Re: Firewall and SMTP

jhunsky wrote:

> I need to secure my network. I would like to prevent SMTP from leaving
> my network unless it comes from one specified server( email server).

OK, that is normally a pretty easy task.

> This should prevent my network from becoming a zombie of spams. How to
> I go about this?

create the following ruleset for your packet filter (whatever device that
is):

from to service/port protocol action
------------------------------------------------------------ -------
email_server any smtp 25 tcp allow
LAN any smtp 25 tcp log + deny


> Will protocol binding do?

Packet filtering will do.

> How do I test if it works?

try connecting to external SMTP Servers from the workstation, look what
happens and watch the logfile.

Wolfgang