[Exim] Security of Exim?

Hi,

I've heard that someone tried to intrude a network by getting to the SMTP
port of the EMail server (Linux / Exim) first to get then to an NT Server.

Does anybody know if there is any security that could prevent this?

Also I know that we can send faked email just by getting onto the SMTP port
(via telnet) - does exim can prevent from this?

cheers
Guillaume