Thunderbird Keeps Threading Emails? Here's the Fix

If Mozilla Thunderbird keeps switching your folders back to Threaded View even after you turn it off, you're not imagining things. This is a long-standing Thunderbird quirk caused by multiple, overlapping view settings.

The good news: you can fix it permanently once you know where to look.

The Real Problem: Too Many View Settings

Thunderbird doesn't have just one "threaded view" setting. It has:

• Global default view settings
• Per-folder saved views
• Per-account overrides
• Special rules for Unified and virtual folders

If even one of these still enables threading, Thunderbird will quietly turn it back on.

Step 1: Turn Off Threading Globally (Most Important)

1. Open Thunderbird
2. Go to View → Sort by
3. Make sure Threaded and Grouped By Sort are unchecked
4. Select Unthreaded

💡 Tip: Do this while no message is selected, otherwise Thunderbird may only apply the change to the current folder.

Step 2: Repair Folders That Keep Forgetting

Some folders store their own corrupted view settings.

For each problematic folder:

1. Right-click the folder
2. Choose Properties
3. Click Repair Folder
4. Reopen the folder and set Unthreaded again

This clears cached metadata that can force threading back on.

Step 3: Stop Account-Level Overrides

Some mail accounts override global defaults.

1. Open Settings → Account Settings
2. Select the account
3. Go to Server Settings
4. Enable "Use global default view settings for this account"

Restart Thunderbird afterward.

Step 4: Watch Out for Unified and Virtual Folders

Folders like Unified Inbox and Saved Searches ignore per-folder settings and always inherit the global view.

Make sure your global view is set to Unthreaded while viewing a Unified folder, then restart Thunderbird.

Step 5: Reset View Preferences (If All Else Fails)

If the issue persists, reset the internal preferences:

1. Open Settings → General → Config Editor

2. Reset:

   • mailnews.default_view_flags
   • mailnews.default_sort_type
   • mailnews.default_sort_order

Restart Thunderbird.

Final Thoughts

Thunderbird's folder view system is powerful but messy. Once global defaults, folder repairs, and account settings are aligned, threaded view usually stays gone for good.

If threading keeps coming back even after all this, the profile itself may be partially corrupted, and creating a new Thunderbird profile can resolve the issue permanently.