IMAP Folder to help clean out spam from inbox

Could I create an imap folder within .mac to drop spam that I might receive from my iphone that finds its way to my inbox if my computers were off? The purpose would be to go back to that folder when back to the computer and mark as spam but this would at least clean out my inbox.

Yes.

Another option would be to use the drone setup. Then SpamSieve would automatically train itself with the spam messages that you move into that mailbox.