I’ve been experiencing this problem a lot lately as every few days even after I’d deleted some email pushed to me from Yahoo! Mail, it would re-appear a few days later saying it had been unread.

I’ve been trying to think of a cause of this, it could be that when I delete mail I don’t give it long enough for it to sync back with the server; but it runs as a background process so surly it can, right?

Or maybe it’s a problem with Yahoo! Mail, which it could be but I’ll be testing out some things to test it and see if I can work all this out as it’s not convenient finding 10’s of emails re-appear.