If you have a desktop Mac, and a Laptop, it’s very likely you use one of them more than the other for email. At least that’s true in my case. If that’s true for you too, then it’s probably also true that Apple’s Mail.app running on your primary machine is a little better at catching junk mail.
Luckily, it’s extremely easy to move the ‘trained’ junk mail settings from one Mac to another. The file you need is LSMMap2, and it’s located in ~/Library/Mail. Simply copy that file from your primary machine, to the same location on your secondary machine. That’s it! Your secondary machine should now have the same capabilities as your primary machine. note: You’ll probably want to make a copy of the file from your secondary machine before you replace it… just in case.
Found via Macworld