'''Problem''' Opening the Activity Manager is opened (Tools > Actvity Manager), then getting messages, the indexing process appears and remains stuck with no progress, never ending. In my case, stuck on some inbox (I have several accounts) at 15%. I searched for a direct fix to find none, until I asked Google this question: "Why does Thunderbird index messages?" The question gave this result: Title: Rebuilding the Global Database "[[https://support.mozilla.org/en-US/kb/rebuilding-global-database|https://support.mozilla.org/en-US/kb/rebuilding-global-database]]". I saw that article referred to a global database file for Thunderbird. To rebuild it requires the deletion of the database file. I did that and the "stuck indexing" issue got fixed. So here is the fix to this "stuck indexing issue" for Thunderbird. '''FIX''' # Close Thunderbird completely. # Locate your Thunderbird Profile folder. It is usually at: C:\Users\(User Name)\AppData\Roaming\Thunderbird\Profiles # Locate this database file: "''global-messages-db.sqlite''" in each profile. # Delete the database file. If you have several profiles, do the same in each one. # Open Thunderbird # Open Activity Manager, and shortly, Thunderbird will show itself indexing messages to rebuild the Global index. This time, it will complete. If it doesn't automatically start, click "Get Messages" and that should kickstart it. '''Cause of issue? ''' Likely a corrupt database file.