pop3 account on zoho does not delete emails on fastmail server

pop3 account on zoho does not delete emails on fastmail server

hi,

I set up a pop3 account on zoho - to retrieve mail from my address @xsmail.com (it's a fastmail.fm address). I ticked off "Delete messages from Server whenever I delete here".

This doesn't work. I originally contacted zoho support and was suggested that I should check with fastmail. Fastmail is now getting back to me saying that it's tested on their side, they can't "see" zoho telling them to delete mail, so I should check whether I've really ticked off that box...

can you please help. Thank you .