I connect to the IMAP service via Thunderbird and have subscribed to several sub-folders. When I drag a message to a folder, Thunderbird removes it from view and it is now seen in the folder. The weird part is that when I then go to the web ui, the moved message is still sittig there in the inbox.

It is shown as a second message in a conversation, the first being the "moved" message in the sub folder.

Any ideas why the original message in the inbox isn't removed?