After the latest Thunderbird update, I lost several folders and their content. I had the same problem a year ago or so and used the following add-on successfully: https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss However, the add-on is not compatible with v. 115.1, the last version being compatible only up to v. 102. Any help would be greatly appreciated as some of the "lost" emails are quite important.