Mac Mail - My POP email's SENT/BIN/JUNK/INBOX has disappeared after Big Sur Upgrade

Hi there,

I have 5 accounts in Mac Mail with my main one the only being POP, all the others are IMAP.

While trying to sort out a folder problem where sub-folders were missing, I lost all my emails but have recovered them I think, through the import Mailbox option. When I set the IMAP ones up, they all have an individual IN/SENT/JUNK/DRAFTS/BIN folders. The POP account doesn't and shows up only in All Inboxes. I've removed the account and re-added it and it's still the same.

If I delete an email to see where it goes, I've no idea but when I search for it by keyword, it says it's in the BIN folder (through the location text top right of email) but I don't know where. I want to add the BIN folder to that account and all the other sub-folders but not sure how.

Any ideas please...

BTW, with the problems I had, I deleted the com.apple.mail.plist file, which some have suggested is as good as re-installing it. It did help in that before I deleted it, any action I did on Mail such as Get New Mail, Compose Message would be queued up (shown by 2 finger click on dock icon).

I have all my mailboxes saved but can't understand why Mail would remove these sub-folders unless it's because it's a POP account.

It's getting to the point now that I will switch to Outlook and only use Mac Mail to refer to old emails, but I'm not keen on that idea.

Thanks