If Thunderbird is downloading multiple copies of incoming messages, it's likely due to incorrect account settings, particularly related to the "Leave messages on server" option, especially if you're using a POP3 account; check your settings to ensure messages are deleted from the server after being downloaded once, and consider compacting your mail folders to clean up any potential indexing issues.
Key points to check:
Account settings:
Go to "Tools > Account Settings" in Thunderbird.
Select your email account and navigate to "Server Settings".
Ensure "Leave messages on server" is unchecked if you want to prevent duplicates on a POP3 account.
Check for corrupted data:
Compact folders: Regularly compact your mail folders to clean up potential indexing issues.
Delete "popstate.dat" file (for POP accounts): If the issue persists, try deleting the "popstate.dat" file located within your Thunderbird profile folder.
Other potential causes:
Multiple email clients accessing the same account: Check if another email program is accessing the same account simultaneously.
Server issues: Sometimes, the issue might be related to your email provider's server experiencing temporary glitches.
Add-ons interference: If you have recently installed any email management add-ons, try disabling them to see if they are causing the problem.
What to do if the problem persists:
Rebuild the mail index:
Try rebuilding the mail index by going to "Help > Troubleshooting Information > Show Folder" and then deleting the "global" file.
Create a new profile:
As a last resort, consider creating a new Thunderbird profile and migrating your data over.
Check for updates:
Make sure you have the latest version of Thunderbird installed, as updates often include bug fixes.
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