@jwz@mastodon.social I appreciate your problem. The only thing I can possibly think of might be IMAP sieve with some magic folders for white- and blacklisting. Imapsieve runs sievescrips (comfigured in dovecot, not user-managable) on the mailserver in response to actions like moving an email. So your people could have magic folders in which they copy/move the email to add/remove the address to the lists, the sieve script should be able to move the email back to where it came from after changing the lists.