This came true. The problem was that email inboxes were inundated with spam, but now free spam filters are good enough to filter almost all spam with extremely few false negatives. (e.g. gmail) Who cares what volume of email traffic is spam?
My point is the same. For a spam filter to be effective it should not penalize you for email you get from a new source that you truly do want.
POPFile on my local machine lets more spam through than I'd like, and has a noticeable level of false positives. Same with the bundled spam filters on my mail accounts at Pair and Fastmail. Whatever we're using at work -- some free filter -- is pretty bad too.
I hear good things about Gmail's filter, but it's not quite free. You have to let Google's computers read your mail, store your mail, and show you ads. I use Gmail occasionally, but checking now, there are still a few pieces of spam on the first page of conversations. (I don't see any false positives among the hundreds of messages in the spam folder, but as I don't receive any diverse/important mail there, that's not surprising.)
Are there any other spam filters you recommend?