Hello, I have a strange problem and I know this is not ThunderBird support but I thought to give it a try. One of my clients has a mailbox 17 GB big and lately he's been having problems with ThunderBird, saying 'The server disconnected. The server may have gone down or there may be a network problem'. Mail get sent but it don't get saved in the Sent' folder. When using webmail (roundcube) there is no problem at all. All the other mail users on the same server have no issues at all. What could it be? The server, of course, being ISPconfig.