downloadMail Plugin: Archive Setting
The folder name format may differ depending on mail client, but two that I'm aware of will prefix them with "INBOX." or "INBOX/" so in your case, you can try "INBOX.archive" and "INBOX/archive".
You can also try looking in your background task log - I believe that if the plugin fails to archive it will output a list of available folders in its task log output.
Let me know if you're able to make any progress; there may be some alternate options to find the folder name if the above doesn't work.
Thank you for your reply. In the end, I switched to a Microsoft 365 account and there seems to be no prefix applied so "archive" worked!
.... there may be some alternate options to find the folder name if the above doesn't work
However I would be very grateful if you could share these alternative options as I often seem to go round in circles with this!
The next step I'd take would be to build a script that connects to the mailbox and runs PHP's imap_list() manually to retrieve a list of all folders. The PHP documentation page (https://www.php.net/manual/en/function.imap-list.php) has a simple example that should work in most cases, and just require swapping in the correct host/user/password.
Let me know if you have any other questions!