Roger Weeks blogs a workaround for a common problem with Mac Mail, one I've noticed but couldn't quite figure out the cause. If you're composing a message and Mail interrupts to tell you it could not save it, then it can't find your Drafts folder. In Panther (Mac OS X 10.3), Mail needed to be told explicitly what the path to these folders was. In Tiger (10.4), Mail displays IMAP subfolders automatically, but still needs to be told about the path in a separate setting. Lame, but good to know the fix.