I keep all my spam and non-spam

I used to do this, but lately I have a combination of things for spam prevention. With Postfix, I have my e-mail address, then the ability to have infinite aliases with no server side changes. So, I sign up for a new web board for example with drakino_newwebboard and I can get the initial e-mail needed to activate the account. Now, if that address gets harvested by someone and I get spam, I tell my procmail file to throw anything to that address away. If needed, I can just go to the board and change the e-mail to drakino_newwebboard2 to keep getting board notices.

Helpes quite a bit for server side IMAP filtering too. I can just say toss anything to drakino_bank into my bank notices folder.