What does local folders have to do with IMAP quota. I think you need to explain a little more. I will guess you are trying to set the archive folder on your providers IMAP mail account to local folders. In account settings, that would look like this <img src=https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-11-02-17-10-13-d6bed3.png> It will not move or copy any mail from the archive folders ion the IMAP account however, just set the default going forward. You will have to handle the movement of that mail manually. Drag and drop might work if you have no anti virus scanner to slow things down. Other wise you might want to export the mail in those folders as MBOX files using this add on. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss You can them "import" the file back into Thunderbird into the local folders location using the addons. It is more reliable than drag and drop.