Using Classic Outlook on Windows for personal email, calendar, and contact management
That is surely to do with a message you have written ready to send not an incoming message, in the "INBOX", that you just looked at, changed in some way by maybe downloading images, and then when yoiu come to close it you cannot save the changes without getting past a n idiotic message that should not happen - i.e. a fault in Outlook of some sort that is now on the 7th page of discusion without being fixed.
If the above IS a cure - its another fault because why would a message in the Inbox get saved to Drafts, its an optyionhaving an effect in an area it should not affect.