Best options are to run all email through a spam killer like Spamcop, or your own Linux mail server with Spam Assassin.
The owner of this board offers hosting, and I think that comes with a spam filter, you just forward to that, and then from that (after spam filtering) to your Berry.
I run my own mailserver with Spamassassin and see no more than 1 or 2 spam emails PER WEEK
