Here are some tips from our customers on addtional spam tests you can add to make Deadletter more effective. To do this, open up the Deadletter settings dialog from the Special menu and enter the text below on the appropriate page (do not include the quotes):

Add to Kill Subject Text page:

Look for "XXX".
Look for "$$$".

Add to Kill Header Text page:

Look for "Emailer Platinum" (a common bulk emailer).
Look for "X-Advertisement".

Add to Kill Message Text page:

Look for "answerme.com" (a common spam response provider).
Look for "EMAIL BLASTER" (another bulk emailer).
Look for "Extractor Pro" (ditto).