How to Fix Thunderbird Says Inbox is Full Error in Batch?

  Rollins Duke
Rollins Duke   
Published: August 18th, 2025 • 8 Min Read

Your Thunderbird says inbox is full? Are you struggling to receive a new email now? Well, it is a sign that now is the time to delete some of the emails or even folders to clear some of your account space. However, deleting the email is not a good idea, as we don’t know when we will need them back again to review some important information.

But if we can’t create an account space and receive new emails, it’s a bad deed because if we don’t get the email on time, it can cost us a lot. So, how can we deal with your situation? Well, we have a perfect way for you from which you can only have advantages.

thunderbird email inbox full error

You can backup your email to your safe place. Well, this way you can free up space without deleting the emails. Yes, we want you to download the emails in a file format that you can access anytime you want to check your emails. Well, we see this as a perfect way to deal with the situation when Thunderbird your mailbox is almost full.

Reasons Why Thunderbird the folder Inbox can’t hold anymore messages

  • Inbox File is Too Large
    Mozilla Thunderbird keeps all the emails of the inbox in a single large file. In case that file gets large, it can stop working.
  • Large Number of Emails in Inbox
    Having hundreds or thousands of emails in your inbox can make Thunderbird think that it is full.
  • Inbox File Is Corrupted
    In a lot of cases, Thunderbird files get corrupted, and the Thunderbird says inbox is full even if it is not full.
  • Problem Of Antivirus
    Anti-virus can also lead to the problem of Thunderbird mailbox full.
  • Account Storage of Email Is Full
    If you are using Gmail, your email provider provides you a limit of storage. If that limit is full, then Thunderbird the folder inbox is full and can’t hold anymore messages.

Manual Way to Fix the Problem of Thunderbird Mailbox Full

Before starting the manual process to fix the problem of Thunderbird mailbox full, you should remember to backup your Thunderbird emails before doing anything to avoid any further issues.

#1: Move Emails Out of the Inbox

  1. Run Mozilla Thunderbird.
  2. Right-click on your email account name.
  3. Choose the new folder and name it “Saved Emails”.
  4. Select the emails from your inbox and drag and drop them into the new folder. This will help you reduce the size of the inbox.

 #2: Compact the Inbox

  1. Move to Thunderbird and click on the inbox.
  2. Then right-click on the inbox.
  3. Now, click on the Compact option.

 #3: Delete the Index File

  1. Close Mozilla Thunderbird completely and properly.
  2. Move to Windows and press Windows+R
  3. Now, type the code: %APPDATA%\Thunderbird\Profiles\
  4. Now, open the folder ending with .default or .default-release
  5. Now, move to Mail\Local Folders\
  6. Check and delete the file with the name: Inbox.msf
  7. Now, open Thunderbird again, and your file will be rebuilt.

#4: Check If the Server Storage Is Full

  1. If you are using IMAP, then move to the webmail.
  2. Look for a warning like “Storage Almost Full”.
  3. Clean Spam folders and large emails to treat the problem of the Thunderbird mailbox full.

#5: Create Archive Folders for Future Use

  1. Use the message and then archive to transfer old emails out of the inbox, or you can press the A key after selecting emails.
  2. After this, Thunderbird will create yearly folders and transfer the messages there. Your problem of Thunderbird inbox is full will be solved.

Drawbacks of Manual Ways

  • Moving emails manually can be time-consuming and a lengthy process.
  • If you compact folders with corrupted messages manually, there is a chance that you may permanently lose them. Therefore, it is suggested to repair corrupt Thunderbird profiles first.
  • You have to keep regular maintenance to avoid the problem of the folder inbox is full Thunderbird.
  • There are chances that you may accidentally delete something important.

Pro Method to Fix the Problem of Thunderbird Says Inbox is Full

Thunderbird email inbox full errors, Thunderbird email quota full, fix these problems with the Thunderbird Backup Tool. With this solution, you can save your emails or even folders on a local drive or even in cloud computing at the same time, so that you can make room for receiving new emails.

What do you think of this path is it appropriate for you? Well, if you think so we are going to give you the full process to help keep your Thunderbird emails secure. We’ll give you a detailed guide, carefully go through each step and see how easy it is to fix the problem with this app.

  1. Install and run the tool on the device first.
    thunderbird says inbox is full
  2. Select the Thunderbird files or folders that you want to save.thunderbird mailbox full
  3. Now, select the save option according to your choice. We suggest you use the PDF format for an understanding of the process. If you want to import the same data into any other email client in the future, then you can also convert Thunderbird emails to PST, MBOX, EML, etc., or the 30+ export options.select saving option
  4. Now, select the destination path and file naming options according to your preference.choose destination path
  5. At last, click on the convert button to save the file locally or to export or transfer it to another email client.export to another email client

Note: You can also save your email in any IMAP-supported account if you want to back it up on a cloud server.

Your Thunderbird emails will now be saved on your selected platform in a few moments. Now you can delete the emails or folders to free up space so that you receive new emails.

Now that you know this app seems perfect to deal when Thunderbird says inbox is full and Thunderbird inbox full cannot receive emails. We suggest you to learn more about it. Well, if you choose this app to solve your problem, you need to know how valuable this app is, and what benefits it offers. So go through some of the tool’s specifications to get a better understanding of it.

Check out Some Benefits of the Tool
  • It Has a Simple UI: Whether you are using this tool for the first time, you can just do the task on it without any difficulty, and all because of its straightforward interface. There is no complexity to mitigate your experience.
  • Save Preferred Mailboxes: Now, in order to free up space when the Thunderbird email quota is full, you need to save some important emails. Therefore, with this app, you can select and deselect which folders you want to save emails from and which not. You can choose them completely freely.
  • Select Data Manually: With this account, you can also select the Thunderbird data manually. If you want to save the emails from the Thunderbird folders and not from the account directly, this is possible with this app. Well, this app is all rolled into one.
  • Secure in Bulk: See, when Thunderbird’s inbox is full cannot receive email, which means you need to clear up a lot of emails. Hence, you can use this app to backup your emails in bulk. It can even save tons of folders to your preferred location and platform at once.
  • File Naming Option: Well, this feature will help you a lot in identifying your specific files after backing them up. You can give different names to different files depending on the date and subject, so that you can easily find them without putting in a lot of effort.

Well, these are some of the most important things that will make your job even more perfect. There are tons of other features you can use to improve your performance. So if your Thunderbird mail inbox full, free up some space by backing it up with this app.

Conclusion

When Thunderbird says inbox is full or you see Thunderbird email inbox full error, it’s time to manage your email. You must first back up your emails in a safe place and then delete them from the account so you can receive new emails. The above-mentioned app is the perfect solution that can best help you. Hence, you have to try it to solve your problem and to have a pleasant experience.

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