I'm running Mail.app on my Mac (Snow Leopard). Two GMail accounts are linked to it using POP. There is an annoying bug which causes certain messages from one of the account to show up in my Inbox. They are always messages I sent to a certain account, and are 6-7 messages from one thread. If I delete them, they just show up again if I restart Mail.app or switch to a different mailbox and back, although the number of messages goes down, until it reaches one, and goes back to six-seven. The only solution I have found is to delete the offending thread from within GMail, except that then another thread takes its place and starts annoying me.