Is sendmail open to relay?

[Mario Jorge Nunes Filipe <mjnf@neptuno.uevora.pt>]

Hi

Some time ago, i was handed the administration of the local mail server.
Unfortunately this is just one of the many things I've got to do and as
such I've never had much time to look through the config's, especially
sendmail.

Today i received several messages indicating that the machine was used
for spam relaying, wich obviously is a cause of great concern both to me
and to the bosses.

The .mc file has a line that says FEATURE(relay_based_on_MX)dnl and i
believed that this would be enough... Apparently it is not... Can
someone please explain me how can i check if the relay is open and how
to fix it. Isn't there a way for me to tell sendmail that it should only
relay mail's from our own domain (uevora.pt).

I know what your going to say, and yes i do have the bat book (right
beside me) but i miss something very important ... TIME.

Thanks for everything

P.S - I do hope that this time someone anwsers me...
-- 
        Mario Filipe 
        mjnf@uevora.pt
        http://neptuno.sc.uevora.pt/~mjnf