When I reply to a message I've received, the reply is put in the Sent folder as I have set that up. The original message I received is also moved there but remains unattached to the reply . It isn't necessary to move it there because the original message is included in the reply message. The original received message should not be moved by Thunderbird until I move it to the folder where I want it to be stored (or I trash it). Usually I trash received messages that I've replied to to reduce storage space and clutter. For a while I didn't know that was happening so I've had to search all my accounts trying to find the original message to file or delete. Lately I've seen a popup that asks me if I want to move the received message and I have to manually uncheck that. It is an annoying extra step. How can I set Thunderbird to not do that?