Resolved Common Errors or Problems in Mozilla Thunderbird

Admin | Email Conversion How to's Software Technology | 5 minutes read | Last updated on February 8th, 2023,

Summary: The article explains the errors and problems that users may face while using Mozilla Thunderbird. These errors sometimes lead to application freeze and later shut down. The processes to troubleshoot petty issues in Thunderbird are also described in this.

Thunderbird advanced by Mozilla Corporation that is a free, open-source application that supports organizing emails, news feeds, chats, and newsgroups quite precisely. It is a desktop-based platform that provides full control and wide ownership over the email messages. If you use Mozilla Thunderbird, there are multiple add-ons presented that you can install and use to customize and improve the emailing experience.

The great thing is that you can easily download, install and can utilize the program for free in the well-defined terms and conditions. Many versions of the application exist that supports Windows, Mac, and Linux systems. Furthermore, the application is presented multiple languages and you can choose your personal localized edition for well understanding.

Despite having multiple benefits, there are few errors and issues that need timely troubleshooting.

Let’s take a look at every problem and their possible solutions:

Problem#1. Thunderbird Cannot Delete Messages.

The main reason behind the lack of ability to delete an email message in Mozilla Thunderbird could be a corrupt trash folder. To fix this, follow the below-mentioned steps:

  1. Click on the Menu button from the top right of the Thunderbird application and open the profile folder. Then, choose the Help button and click on the Troubleshooting Information. In the displayed Troubleshooting Information option, then press on the Show Folder button presented under Application Basics. The windows will show the profile files.
  2. After that, close the Thunderbird application
  3. In the File Manager tab, open Mail folder or ImapMail folder (as per POP or IMAP account you are utilizing)
  4. Now, open the folder with the received mail server name (like or
  5. Choose Trash and MSF files and remove them. In multiple accounts, this file is named Deleted or Bin
  6. Then, restart the Mozilla Thunderbird application
  • In the case of IMAP, a new Trash folder will mechanically be created by Thunderbird app.
  • In a case of POP, go to the Folder List and then right-click on the account name and choose the New Folder. After that, give the folder name as Trash and hit on the Create Folder to confirm.

In case the error or problem carry on and you fail again and again to delete the email messages that are no more necessary, you can choose an alternative option to change the emailing application to Microsoft Outlook that is fairly proficient and organized. To use MS Outlook, you will require to transfer all the email data from MBOX to PST files.

Problem#2. Thunderbird unable to Send Email Messages

If you are not able to send email messages from your Mozilla Thunderbird account, there can be two causes behind this:

  • Wrong Thunderbird Settings
  • Blocked Port 25 by Internet Service Provider (ISP)

To fix this issue:

  1. Make sure that Thunderbird Settings are correctly configured.
  • Incoming mail server (POP3/IMAP server):
  • Outgoing mail server (SMTP server):
  • Username: the complete e-mail address such as
  • SMTP authentication should be enabled for the login to be precise.
  1. Try utilizing alternate TCP port 2525 for SMTP Server.

Note: If you fail to resolve this problem, you can move email and other items from MBOX to PST file format for using ease functionality of Microsoft Outlook.

Problem#3. Thunderbird Cannot Receive Messages

If the Thunderbird program fails to receive email messages, then check whether the account is configured inappropriately. To check Thunderbird account settings:

  1. Choose Tools and then hit on the Account Settings
  2. From the list that shows on the left pane, choose Server Settings
  3. You can view the configuration settings at the top of the page to verify the connection to the incoming mail server
  4. The email account provider provides you connection details about the servers. Just make sure that the account settings match these settings.

Problem#4. Thunderbird Closes Unexpectedly

When Thunderbird closes suddenly, the problem is raised to as application crash. When it closes unexpectedly, Mozilla Crash Reporter opens. Various reasons are liable for the crash: so, the better way would be to post-crash report ID.

Otherwise, attach a mass trace in the bug report or any forum. This will help resolve the major reason. Converting data from Thunderbird to PST format will help rectify the persisting problem and perform continued functionality.

Problem#5. Warning – Server doesn’t use encryption

Initially, verify if the server supports encryption. If it does then you may need altering Thunderbird settings. Hit on the Change Settings option and then apply correct settings

If the mail server doesn’t support encryption, then, you can use it at your personal risk. Check the box connected to I Understand the risk and hit on Create Account option. Otherwise, switch to the mail service provider that gives a secure connection like Yahoo, Gmail, etc.

Start Thunderbird in the Safe Mode & Resolved Thunderbird Errors or Problems

You can start Mozilla Thunderbird in the safe mode to troubleshoot continuing errors and issues. In the Safe mode, you can reset settings of Thunderbird application or disabled the add-ons that are generating problems. To verify it’s the error is being reasoned by a particular add-on, try relating application behavior in the Normal mode to that of the behavior in the Safe mode.

  1. To start Mozilla Thunderbird in the Safe mode, follow the steps below:
  • When Thunderbird is not running: Press and hold down the Shift key while starting Thunderbird to open it into the Safe mode
  • When Thunderbird is running: Hit on the Help menu from the top of Thunderbird application and then choose Restart with Add-ons Disabled… menu item. After that, click on the Restart in the dialog box
  1. In the then displayed Thunderbird Safe Mode dialog box, press on the Continue in the Safe Mode option to complete the task to start Thunderbird in Safe Mode.

As discussed above there are different problems and Mozilla Thunderbird errors that a user preserves on come across on a daily basis. So, to avoid all kind Thunderbird issues forever, a user is suggested to move to some other email application like MS Outlook. It is also one of the most effective e-mailing programs with multiple responsive features and function.

The Concluding Words

As all the issues discussed above related Thunderbird program, a user is suggested to switch to Microsoft Outlook. Now, to resolve Thunderbird issues and errors, a user is moving towards Outlook. So, to achieve this conversion successfully, a user is suggested to use Thunderbird  Converter and transfer all the Thunderbird mailboxes to MS Outlook within a few numbers of clicks.