Create folders for the different types of mail -- "Friends", "News", etc. and they will sync. Don't put them under "on my mac", the list should be lower down. Not at the mac right now, but I think if you click on "File" or "Edit" on the menubar you will be given an option to create a new folder. I have done this, created rules to automatically move mail to the proper folder, and they all sync to my iPod, iDisk, etc. (using IMAP mail, obviously).