Hello there Manuele Florenza. We have read your message We try to help you. Could it be that you have msf index files and also the mail files in another location, for example in your inbox? try to find them and copy them to the pop-server folder and the folders re-appeared on the left of the thunderbird application directory structure. They may have forgotten to repositioned (re-arrangened) them after an update? It is an option, so it could be that these files are out of place beyond the fact of your Thunderbird .exe icone Back in place you can also delete the msf file and then restart the Thunderbird software and it will rebuild the entire index. Greetings Firefox volunteer.