Hi, do the emails still come back after you clear both Inbox and Drafts?
Go to Outlook on the web, open Settings, Mail, Rules and delete all rules. Then check Mail, Forwarding and turn it off. Go to General, Mobile devices and remove unknown devices. After that, change your password and sign out of all sessions. Finally, empty Drafts, Inbox, and Deleted Items, then refresh the page to stop the loop.