Blacklist mail

[Johnson, S]

A few months ago I created a fake user and advertised it in a hidden
mailto on our home page.  It took a few weeks but I'm getting good spam
messages being dropped into this box now.  I know I can use the learn
function to pull the messages from my exchange server, however I know
these messages are strong spam.  Should I just use the learn function or
is there a way to blacklist the servers sending these messages? (or is
there a better method?)