"As innovative and as good as it is, Apple's Junk Mail feature built into Mail 1.2 is not perfect. The best example: This morning I found one of the noted "Nigerian" spam messages in my In box, despite having Junk Mail set up to filter and move spam automatically to the Junk Mail folder. I also offer a quick word of warning if you have set your Junk Mail to automatically go into the Junk Mail folder. Check that folder now and then as your Mail program learns better what is and what isn't junk. Yesterday I found a critical work email message in the Junk Mail folder. Of course, Mail was right on in moving 14 other spam messages to the Junk Mail folder. Progress!" [Mac Net Journal]

I have been using Jaguar for about a week, and little by little the junk mail filter seems to learn better and better. This same kind of wrong classifications happen every now and then.