One of my inbox and sent folders (for one particular email address) lost most of its contents. I was able to recover the contents of the inbox folder by using "repair" under "properties" of the folder, but it didn't work for the sent folder. I've tried importing and restoring backups to no avail. I noticed a big change in the size of the folder in a series of Acronis backup files, but can't seem to bring the contents of that backup into Thunderbird. I've tried creating zip files and importing, but nothing works.