I have specific old email addresses that are always 100% spam. They are old users who in some cases have been gone from our organization for years. By default, I have a bunch of "internal honey pots."
As a feature add request, I would like to see "buddy block" functionality where I could put multiple email addresses into a block list, and if an email is sent to something on this list, any matching email to another (legitimate) user would get blocked.
I often get spam blasts of the same exact message to 20-30 different people, 10-20 of which are no longer here. A buddy block list would kill a huge amount of the "mutating" spam where spammers are changing both IP addresses and domain names every 3 days, but are sending the exact same messages over and over.