Deleted E-Mails keep reappearing in Inbox

Deleted E-Mails keep reappearing in Inbox

Hi- in brief the issue is I run Zoho Mail across laptop, Phone and Tablet, all synched and problem free until 3 days ago. Whichever device I use to delete e-mails the deleted mail, upon refresh (or opening on another device) reappears as a new mail. This even happens on the same device- ie I delete an e-mail, I re-open the mail app (or refresh) and it's there as a new mail in the Inbox..any ideas?

Thanks