Spam with our domain

[Paul Douglas Franklin of Yakima UGM]

We have been receiving spam from randomusernames at yugm.org.  These are 
names which do not match any real users.  This spam did not originate on 
our server; it has been relayed at least once.  Can anyone point me to 
some method of screening it out?
--Paul

-- 
Paul Douglas Franklin
Computer Manager, Union Gospel Mission of Yakima, Washington
Husband of Danette
Father of Laurene, Miriam, Tycko, Timothy, Sarabeth, Marie, Dawnita, Anna Leah, Alexander, and Caleb