[Fixed] Thunderbird Keeps Downloading Same Email: IMAP & POP

With the outdated Mozilla Thunderbird version the users encounter the issue that- “Thunderbird keeps downloading the same emails”. Causing issues such as: unorganised mailbox, very large profile size, and even mismatched sync over Thunderbird desktop & android application. 

Although the Thunderbird duplicate emails issue is more common with the POP3 accounts configured – it can also occur with the IMAP accounts. Here we have listed the possible causes – why Thunderbird is repeatedly downloading the same emails continuously and troubleshooting fixes for better performance of applications. 

Symptoms of Thunderbird Duplicate Emails Issue

• Inbox and profile size suddenly increases unnecessarily
• The status bar always showing hundred of emails downloading at once 
• One email is in the multiple folders (eg: Inbox, Spam, Trash) simultaneously
• Thunderbird performance getting slow or degraded 

Thunderbird downloading duplicate messages although seems harmless on the surface can lead to much larger loss of emails if caused due to profile corruption. 

User Query: Thunderbird Downloading Duplicate Messages Issue 

“My mailboxes are filled up with duplicate messages, sometimes 10+ copies of each one. I haven’t changed any settings on the server or in Thunderbird, so I’m not sure what is causing this.” 

Fix Thunderbird Keeps Downloading Same Email Issue 

The mozilla Thunderbird mail duplication issue is often caused due to reasons like – account misconfiguration, corrupt index files and even mismanaged imports. It can be easily avoided and fixed by taking the below given precaution in mind and following the instructions. 

Fix 1: Repair MSF Files 

In the Thunderbird email header and location information is stored as MSF (aka Index) files. Thunderbird may display duplicate messages in multiple folders due to corrupted index files. It can happen to both IMAP and POP Account configured in Thunderbird. 

1. Open Thunderbird on your computer. 
2. Right-click on the folder in which you are facing duplicate issues. 
3. Choose Properties.
4. Click on the Repair Folder option. 
5. Press OK.

Repeat the process with multiple mailboxes if the mail duplication issue, and throughout the entire profile. 

Fix 2: Verify POP3 Server Settings

If settings like “Leave messages on server” (only with the POP) are misconfigured Thunderbird keeps downloading the same email. 

1. Shut down Thunderbird.
2. Click Menu >> Troubleshooting Info >> Open Profile folder.
   ( C:Users<User>AppDataRoamingThunderbirdProfiles).
3. Go to the “MAIL” folder. 
4. Search for the file popstate.dat.
5. Delete the file and restart Thunderbird to fix the issue. 

Fix 3: Update to the Latest Thunderbird Version 

Older Thunderbird versions use legacy program files which may make the program unstable that can further lead to duplicates. To fix the issue, update to the latest version. 

1. Open Thunderbird. 
2. Click on Hamburger Menu >> About. 
3. Restart Thunderbird the latest version. 

After Imports, Thunderbird Duplicate Emails Issue May Appear 

Many users repeatedly get Thunderbird downloading duplicate messages after importing data from other email clients or email servers. The issue can be avoided easily: 

• Ensure you have a stable internet when importing data (specifically when moving them to other folders).
• Import in batches to avoid duplicates. 
• Do not import another file unless the previous sync is completed. 
• Creates a new destination folder for import. 
• Avoid using the force refresh i.e. via the get message button during the import 

Fix 4: Verify the Folder Sync Settings (Only IMAP) 

1. Open Thunderbird. 
2. Click on the Hamburger Menu. 
3. Open Account Settings >> Synchronization & Storage.
4. Uncheck “Keep messages in all folders for this account on this computer” 
5. Click “Advanced” to uncheck the unnecessary folder to avoid usage of Thunderbird resources.   

Fix5: Disable Interfering Elements 

Proxies, antivirus, firewalls, and Thunderbird add-ons can interfere with how Thunderbird deals with data.

• Use a secure private email connection
• Temporarily disable firewall for emails (in Windows) 
• Start Mozilla Thunderbird in Safe More to disable all add-ons at once. 
• Disable antivirus to check if the repeated email download issue has stopped. 

Fix 6: Remove the Duplicates Emails in Thunderbird 

If your mailbox size is increasing due to the large number of duplicates in Thunderbird you must remove it for efficient performance. 

You can manually remove the duplicate emails however it may lead to do so. 

Thus beforehand one must backup their Thunderbird profile before deleting the emails. 

Easier Ways to Remove Duplicates from Thunderbird 

You can remove duplicate emails from Thunderbird  and further build a fresh Thunderbird profile and resolve the Thunderbird keeps downloading same email issue: 

Method 1: Using Free Add-On

1. Open Thunderbird on your PC.
2. Right Click on Menu >> Themes & Add-Ons. 
3. Search for Remove Duplicate Messages. 
4. Click on Add. 
5. Open the Mail. 
6. Go to Tools & Click Remove Duplicates. 

Note That: It will only work one profile at a time and is not compatible with all Thunderbird versions. It does possess minor risk of data loss as it is not 100% designed for enterprises & professional usage. 

Method 2: Thunderbird Duplicate Remover Tool: 

It is a dedicated offline software application that you can install separately to remove duplicates from multiple profiles Thunderbird with an option to selectively choose mailboxes & other advanced filters on all Thunderbird versions. 

Tip: Users must regularly compact their Thunderbird folders to avoid having the Thunderbird keep downloading the same email issue. 

Note: Many experts also suggest to start using Thunderbird in the offline mode to fix the issue. However it is not a permanent solution. 

FAQs: Mozilla Thunderbird Keeps Downloading the Same Message

Q1: Why does the activity bar in Thunderbird always show downloading messages? 

There can be a few reason what Thundebris may show downloading messages over a long period of time such as: 

• Large Mailbox 
• IMAP Synchronization Issues
• Improper Email Migration

Q2: How do I stop duplicate emails in Thunderbird?

• Ensure the correct configuration of IMAP & POP account 
• Timely compact Thyndebrid folders. 
• Archive Existing Emails from Server (If Needed)
• Stay Away from frequent account reconfiguration

Q3: Is it safe to delete duplicate emails?

Yes. In fact it improves Thunderbird performance by reducing the mailbox size and getting rid of Ghost emails. 

Conclusion 

Thunderbird keeps downloading the same email list in Inbox, is not permanent and can be easily resolved manually by Thunderbird account settings modification or by using the addons & third-party software. Although if the issue persists, you can consider migrating Thunderbird to other reliable email clients like Outlook, Mailbird, and even switching to webmail for a better experience.