[Cialug] Hijack This! (Equivalent on Linux?)

[Andrew Lietzow]

Cialug'ers,
I've both done a lot on this problem, and not near enough.   Some idiots 
in the world have decided to hijack my server as a Relay host for 
Spam.   I have only three entries in my /etc/mail/relay-domains listing, 
and these entries are NOT the domain from which they accomplish this spoof.

I am using sendmail 8.13.1.  Have not had a problem with this in the 
past until recently.   Apparently, I've relaxed my controls but I can't 
understand how they can relay if I haven't enabled it.   I thought 8.9 
and above defaulted to relaying denied? 

I'll keep digging but help is much appreciated.   I'm getting hundreds 
of messages about bounced mail and that is how I discovered them. 

TIA,

Andrew L.