Copying junk mail filter to another computer

I just got a new MBA. I use Apple's mail program. My desktop iMac is pretty good at filtering out junk mail. Is there a way to copy what my iMac has "learned" over to my new MBA? i.e. where the heck is the junk mail filter database stored? Is it in a preferences file? Is the file something I can transfer to another computer?

The iMac is using Snow Leopard; the Air is using Lion.

Thanks!

Dan