Strange problem indeed.

One thing I can add to this thread is that by default the Pocket Outlook application leaves a copy of messages on the server. Downloading mail to the PPC will not remove it from the POP server. If, however, you choose to delete a mail message from the PPC, it will send the delete request for that message to the server.

There is no way to remove individual mail from the PPC while keeping it on the server. You can remove all mail messages from the PPC without deleting them from the POP Server by using the Clear all Messages option in Options.

As for Gmail specifically, it sounds like Gmail automatically removes mail from its servers once any POP client downloads 'full messages' (rather than headers only). I can see why they might want to do this since it keeps email space requirements down.

-Rick