POP doesn't function very well with 'leaving mail behind' because that's not what it's designed for. There are hacks to do it, but there is special magic required in the client and a lot of them don't care. That's why Yahoo fetched all the email you have ever received: because as far as the server is concerned, you *haven't* received it yet. Even though Evolution is able to give you the fiction that you have.

Wade.