If you have a version 68 profile, either as a backup or because you have not yet updated to version 78, we could use your help, to test how well the newest 78 does the update, particularly with regard to address books.

NOTE: after you update to 78 you should not use the profile with version 68.  You will want to have used a copy of version 68, or restore a backup of your profile. The version 78 upgrade process changes address book format to a database (from mork).  As a result, it will rename .mab files to .bak.

Start with your version 68 profile, and install version 78.  If version 78 isn't using the profile with the version 68 data (which it probably is not), you will want to switch to that profile with Help > Troubleshooting > About:profiles   For additional guidance see https://support.mozilla.org/en-US/kb/dedicated-profile-thunderbird-installation and  https://support.mozilla.org/en-US/kb/using-multiple-profiles

Some things to check:

• All address books have been migrated
• Contacts look OK
• Whitelists in account settings are correct
• Filters which reference address books are correct
  
• Filteres which reference folders are correct
  
• Performance is good