Can I bring my old mails with me when downgrading from Mountain Lion?

Recently upgraded my MacBook Pro from Snow Leopard to Mountain Lion which I hate. Battery life has been more than halved, even with the 10.8.2 update, the computer runs extremely slow now and it keeps dropping wifi connections.

So I called Apple and ordered a Snow leopard installation disk and I have now backed up everything in my "user" folder (which is pretty much everything).

One question remains before formatting the hard drive and installing a clean SL:

How do I make my old emails in Apple Mail survive the operation?

Thanks,