A new install of ubuntu mate 16.04.03 and thunderbird. I have an imap account with multiple folders. When I drag a message from one folder to another on the imap server (or if I use the 'move to' menu option) the message usually disappears from the original folder, but doesn't appear in the new one. The message has been moved correctly (I can check via a webmail), and if I close and restart thunderbird it appears when I browse the folder it's now in, but no amount of checking for mail or browsing to the folder makes them appear without the restart. All the folders are synchronised offline. I used to have this happen on my old machine running 14.04 as well, however it was infrequent so having to restart wasn't so bad. Now moving a message rarely works properly.