Yes, I do have "leave the mail on server" checked to allow the message to be retrieved on multiple computers. Normally in the past and with other mail programs, including TBird2, each computer would only ever download one copy until the message was deleted by myself. This has only happened with TBird3, on my main computer, when it went through the upgrade a while back. Kmail on the same machine functions properly and will only ever retrieve one copy. I've googled quite a bit and it appears quite a few people are having similar problems and problems with multiple folders etc. Although short of installing an add on to remove the messages after the fact, I've not found a solution yet.