You don't have to delete from the server. Gmail supports IMAP, and if you set Thunderbird to cache the whole account, even if Google locks you out your entire offline cache is safe (and can be copied into another account if necessary).
Right, but I don't necessarily want alll of my messages vulnerable to compromise. Once I've deleted it from the server, I don't have to worry about somebody getting into my account, or the possibility of unscrupulous practices by Google.
