Mozilla Thunderbird won’t open in Windows [Fix]

By: Ivan Jenic
2 minute read

Mozilla Thunderbird is one of the most trusted email clients on the market available on various platforms used as not only as an email client but also as an RSS feed and much more. And the best part? It’s an open source project.

However, even though this email client is frequently updated and well-coded, users are experiencing a number of issues with the software. One of those issues is critical and is related to sudden crashes after the start up. For that purpose, we prepared a simple but useful workaround that should help you resolve it.

How to resolve the ‘Mozilla Thunderbird won’t open’ issue in Windows

The simplest way to address this issue is by deleting the ‘parent.lock‘ file found in the profile directory. You can do that by following these instructions:

  1. Close Mozilla Thunderbird.
  2. Right-click on the taskbar and open Task Manager.
  3. Under Processes, find and kill all Thunderbird-related processes.
  4. Now, press Windows key + R to bring up the Run command.
  5. Type %appdata% in the command line and press Enter.
  6. Open the Thunderbird profile folder.
  7. Find and delete the parent.lock file. You may need administrative permission to do so.
  8. Start Thunderbird again. It should now function without any problems.

However, if the problem is still there, try running the client in the safe mode (without add-ons) or performing a clean reinstall. To start the Safe mode in Thunderbird, navigate to Start and click on Mozilla Thunderbird (Safe Mode). On the other hand, there is an alternative way to enter the Safe mode:

  1. Press Windows + R to bring up the Run command.
  2. Type thunderbird -safe-mode and press Enter.

If you need to reinstall the client, make sure to delete all of the remaining data in Profile folder and Program files. You can do so manually or with a 3rd-party uninstaller. Either way, you’ll start from a scratch without the issue.

If you have any remarks or questions regarding the subject, use the comments section below!


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