Much of the diagnostic detail relating to emails is buried in locations that you can’t see. If you have the need to examine email messages for troubleshooting or security this can be a challenge.
A great tool you can add to your arsenal is the free Message Header Analyzer which you can find here:
Once installed you will find an additional button in your OWA:
That when selected will give you a range of options you can use to dive deep into the technical information surrounding the email in question.
I especially like the ability to dig into the SPF and DKIM style details.
If you need in to do any troubleshooting or email analysis on a regular basis I’d highly recommend you add this to your inbox.