Drag Drop seems OK providing there is not an All Mail folder eg gmail in which case the email must be deleted from this folder if you don't want it kept on the server.
When I use T'bird Local Folders I copy the incoming mail to a T'bird folder and then delete the original. I do not retain mails at server other than what is currently active. Also I do not use threaded conversation which links all mails with the same heading ... whatever sender.
My lady uses T'bird but keeps using drag and drop for incoming mail to a T'bird Local Folder ... which is logical thinking. But I think this has issues
