Is it possible to retrieve the RFC 2822 (or any) headers from an email with the Outlook/Office 365 REST API?

UPDATE: The InternetMessageHeaders property was added to the beta endpoint of the Outlook API, so you can get this without using the extended property stuff. You do have to request the property explicitly via $select though. Something like: GET $select=Subject,InternetMessageHeaders For Graph: The property also exists on messages in the beta endpoint for Graph, … Read more