I can't seem to find a way to fetch raw RFC 2822 email headers from the message resource https://msdn.microsoft.com/office/office365/APi/complex-types-for-mail-contacts-calendar#RESTAPIResourcesMessage
All the standard headers To, From, Subject are available. How do I get a list of headers[] other than the standard once such as "Received", "Delivered-To", etc.. Is this feature not yet supported?