https://blog.thunderbird.net/2023/07/our-fastest-most-beautiful-release-ever-thunderbird-115-supernova-is-here/

I regret you had a problem, but upgrading is generally problem-free. I do recommend periodically backing up one's profile, as that is a guarantee against losing data. There have been many changes since ver 68, so I suggest you review the 2023 release of ver 115 at https://blog.thunderbird.net/2023/07/our-fastest-most-beautiful-release-ever-thunderbird-115-supernova-is-here/ and the 2024 release of ver 128 at https://blog.thunderbird.net/2024/07/welcome-to-thunderbird-128-nebula/ Finally, Thunderbird now has TWO releases, a monthly (ver 136) and the extended support release (ESR) which is 128: https://blog.thunderbird.net/2025/03/thunderbird-release-channel-update/ If you want to continue getting periodic, but not monthly updates, I suggest getting the ESR release, other wise, the monthly (default) at https://www.thunderbird.net/en-US/thunderbird/all/ Thunderbird routinely makes update changes internally to profile when updates are done on a regular basis. Since you will be leaping from 68 to the current 128 or 136 release, some manual changes may be needed. The primary one is that the addressbook has been converted from a MAP file to an SQLITE file. After updating, I suggest clicking tools>import>import from a file and then selecting addressbook and then selecting MAB and the locating and selecting the abook.mab addressbook from your profile to update it, followed by doing the same for your history.mab file. Once done, I encourage doing a backup of the profile. Assuming windows, here are the steps ( I also include the restore steps - just in case...) '''BACKUP''' # ensure thunderbird is not running # enter %appdata% in search window on task bar and press Enter key # this should open windows file explorer in Appdata\roaming folder # highlight the Thunderbird folder and copy to external media '''RESTORE''' # ensure thunderbird is installed and NOT running # enter %appdata% in search window on task bar and press Enter key # you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it # start thunderbird and all should be there