Some IMAP providers have dedicated folders for use that cannot be removed. They are generally harmless and success in removing them might compromise the email service. However, you never mentioned the names of the folders; knowing that may cause a better response to appear here.

Thank you for the reply. I doubt that it is an IMAP provider issue because the holder relates to outlook.office365 and Microsoft prodded around my computer for about four hours and you would think that they would know if their IMAP servers were preventing it deletion. I deliberately refrained from mentioning the folder names because they are in Italian and I think that would likely lead us into blind alleyways. However for your info the folders are Problemi di sincronizzazione, errori locali, errori server and conflitti. I suspect that they are office 365 app folders which may have been installed when I bought a recent Home and Student Office 2021 licence (from Microsoft). Where the Italian folders came drom I have no idea as I didn't install any Italian version although I have dabbled in Italian in the distant past but I think the Italian-ness would be a red herring

Just a possibility: highlight the account in left pane, rightclick and select 'subscribe' option and see if you can unsubscribe from those folders. If so, that should make them disappear.

Thanks David - you were CORRECT I struggled to find the unsubscribe option then took a while to realise I had to dispaly only the subscribed folders

DELETED