After the last update (12.0.1) I opened TB Portable and all my e-mails were vanished. I didn't really worry because this wasn't the first time and last times always managed to fix it. I have found a backup of prefs.js file and replaced with the one in the profile folder, assuming I'll see my e-mails when I restart TB Portable. It didn't work. The most annoying part is after replacing prefs.js, my 15.6 GB large TB Portable folder is now only 2.1 GB.