test for SMTP relay

What is the best way to test for smtp authentication, relay etc.

If evolution was set up to connect to @domain.name.com with a pop
username and password and smtp was setup to connect to the
@domain.name.com smtp server. Once they were authenticated for pop
could they then send smtp messages from another program not evolution
this being a virus of sorts that is now trying to latch on to the
connnection created with the pop authentication.




Jim