I get a lot of spam. Not counting the spam that is addressed to non-existent recipients within my domain (which numbers in the order of 10 to 20,000 per day, all piped to /dev/null), I get probably 2 to 300 spams every 24 hours. For some time, Bogofilter has been working hard to keep the proportion of those spams reaching my inbox as low as possible.
Since becoming a Mac user, I've moved the bulk of my email receiving and sending from Mutt to Apple Mail. This has had two consequences: I no longer train Bogofilter anywhere near as actively as I was doing 12 months ago, and I now rely on the spam (or "Junk") filtering capabilities of Apple Mail. (I suspect I am also sending a lot more HTML mail, which does bother me.) This morning, for example, Apple Mail downloaded 77 emails from the IMAP server, and presented only 5 of them. In other words, it filtered out 72 spams that Bogofilter missed. Now, this is less an indictment of Bogofilter than it is praise for Apple Mail—since I am rarely providing Bogofilter with ongoing training, its effectiveness is just decaying over time as would be expected as spam evolves. I would estimate that I see less than five false negatives (spam in my inbox) per day, and I can't remember the last time I saw a false positive, though I don't check for those as often as I probably should. Apple Mail has good spam filtering.