From: IN%"unicorn@schloss.li" "Black Unicorn" 24-MAY-1996 20:51:51.95
Nothing. Perhaps block e-mail from the address the threat mail was sent from after a certain number of legitimate complaints.
This, of course, depends on the threats/whatever being sent to the remailer in question as a 'first in chain' mailer.
It also depends on the remailer being able to tell that the messages in question came from a particular address. If the messages are encrypted with the keys of the other remailers in the chain (as should be the case for proper privacy, etcetera), then there's no real way to tell for many cases. About the only exception would be recognizable spam, all being sent along the same remailer path (notice that lots and lots of mail is being sent from an address, and is going out to the same other remailer).
Ask the recipient if he or she wishes all encrypted mail addressed to his or her key to be supressed.
This is a version of the final remailer blocking mail to a particular address, at least using the possible means (see above). -Allen