I'm migrating someone from having their email on a standard Linux VPS to Gmail for Business. That part's easy, done it many times, all done. The person however uses a Mac which I'm not that familiar with, and their email was downloaded to the machine using POP rather than IMAP, so I'd appreciate some pointers on a few things.

There are 30,000 odd emails on the mac, including around 25,000 spam.

 1) Can Mac Mail do spam filtering? Is it reliable? I'd like to knock out the spam before moving the actual useful email up to Google.

 2) I tried adding the Gmail Apps account alongside the existing account. Both have the same email address, but different servers - one is mail.domain.com (which is correct) and Gmail was added by the mac mail wizard so should hopefully be hard coding in "imap.gmail.com" rather than "mail.domain.com". It said "invalid credentials" or similar. Any thoughts? I may have to add manually, which should be easy enough, but remoting into a mac laptop was slow and I'm not that familiar with the interface.

 3) Any suggestions how to actually migrate the email up? On thunderbird I'd just right click, choose copy to, then the account.

I'll probably have to get myself a virtual mac to try some of this stuff out, I found www.macincloud.com which should do the job for $1/hr.