It is a PITA to have to go to my web control panel to blacklist senders one by one.
It should be dead simple to have an option, when confronting an individual e-mail or better yet, the spam or junk folders, to have a dropdown or right-click menu option to BLACKLIST the sender. Right then, right here, no need for separate login, separate cut/paste or type in (with inevitable errors) each offender.
DEAD EASY. Squirrels are smart enough to keep track of hundreds or thousands of caches nuts; squirrel mail should be able to keep track of hundreds or thousands of unwanted senders EASILY.
It needs to happen at server level because doing it mail app by mail app does not cross platforms well when accessing via different devices/apps/platforms.