I'm trying to use Microsoft Graph to get the original email address a message was sent to if it ends up there via BCC.
We're using MSGraph to get emails sent to a shared email inbox in the form of "AppInbox-1234@example.org", where "AppInbox" is the name of the shared inbox and "1234" is an id we use in the app. We have a rule that already moves the email to the shared "AppInbox", which in turn fires off our subscription that looks at the recipients and uses the ID to store contents the message.
This works great if the email address is in the "To" or "CC" fields. But if the email address is the "BCC" field, I can see the email itself, but not the address it was originally sent to (e.g. "AppInbox-1234@example.org"), which I would need for the ID.
When I look at the message itself I only see the empty collection
"bccRecipients": [],
The best lead I've had seems to be around ExtendedProperties, but I haven't been able to figure out how to get the original recipient.