I would be glad to help you test the theory, by sending you a message, then deleting it before you read it, and you see if it's gone or not. Consider it done. Look for PM from me, but don't open it.
look for a message from me, if you see it, it won't help to delete it, because I deleted it before you read it. It's sitting there with an "undo" if I want to undo the delete in my outbox. you should not see it if it works to delete it before someone reads it.