你说得对，目前没有办法.访问标头(甚至完整的 MIME)肯定会很有用，我会确保它被传递.

I am using the rest API documented here https://msdn.microsoft.com/office/office365/APi/mail-rest-operations and https://visualstudiogallery.msdn.microsoft.com/a15b85e6-69a7-4fdf-adda-a38066bb5155 to analyze e-mails in an application. When I "View message details" in Outlook I see the header fields for:

Message-ID: <1421862991001.54993@domain.com> 
References: <1421861073749.70076@domain.com> 
In-Reply-To: <1421861073749.70076@domain.com> 

Is there a way to access these fields through the rest api? The api returns a ConversationId and Id, but those have different values and nothing that can give the context of a message like In-Reply-To does. I realize since these fields aren't documented my answer will be no, but perhaps there is some other way?

I realize this isn't a great example of a programming related question, but I've read this is the best place to interact with the developers at MS responsible for these APIs.

You're right, there isn't a way currently. Accessing the headers (or even the full MIME) would definitely be useful, I will make sure it's passed along.