I am responsible for maintaining a couple of small business' email server.
I currently use FreeBSD, Sendmail, Procmail, and Spamassassin. (Apache as the web-server along with Squirrelmail.)
While writing a procmail recipe is easy for me, the average end-user is never going to be able to ssh into the mail-server and edit their own procmail.rc file.
I would like to add a feature that adds to the bottom of their emails some sort of 'footer' that will be appended to their messages for them to click on a link and perhaps say; "Add This Sender To Whitelist" or "Block This Sender" - and then update their procmail recipe.
Any suggestions on how to accomplish this?