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Clean some space if the space on servers is over the allowed limit.Re-build the Thunderbird profile folder to fix the issue (and probably other issues as well) Try to set it as “remove it immediately” under Tools –> Account Settings –> Server Settings –> ‘When I delete a message.’ This will instantly ping the server to start syncing and update any changes made. Some servers don’t respond properly if there is a delay between a change in client and the syncing with servers.If it is, use a different folder than the one you’re trying to delete. Check under “Tools” –> Account Settings –> Copies and Folders if that’s the case. So if the folder is empty and you are trying to delete it, Thunderbird cannot get rid of it. Some folders are necessary for Mozilla Thunderbird to function.Make sure you don’t delete the cache folder altogether just the contents inside it. If there’s a cache on your IMAP folder, you should delete the contents from the cache folder from the web-based email interface first and then come back and delete the folder in Thunderbird.
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The only solution is to try to the web-based email interface by directly logging into your email provider and deleting that folder from there.
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