Status (by robm at Sun Feb 23 23:18 UTC)
So after accidentally rolling out a rule in error last week (http://status.fastmail.fm/2014/02/20/increased-spam-due-to-spamassassin-error/), that caused some very likely spam to have a low score, the maintainers of SpamAssassin made another change to the rule scoring the other day (http://www.gossamer-threads.com/lists/spamassassin/users/183590#183590).
Unfortunately this change was incompatible with the previous change we made to fix their error. This caused messages that were deemed to be very likely to be spam by the bayes db to have a very, very high score, even in cases where sites have a whitelist score that would normally bring them under the spam threshold.
The net result, it’s possible that some people will see quite a bit more email incorrectly marked as spam in the Spam/Junk Mail folders over the weekend. We recommend you check this folder and "Report non-spam" on these items to move them back to your Inbox.
We’ve reverted our change now, which should fix this issue, but hopefully the SpamAssasin maintainers are a bit more careful in the future.