OptionalCCOptionalCreatedDate and times associated with the message
OptionalExternalOptionalLastOptionalReceivedOptionalReplyIn some providers, such as MS Graph, replies can be sent to multiple other recipients rather than just the original sender
OptionalSentOptionalSubjectOptionalThreadThe ID of the thread the message belongs to
OptionalToAll To recipients of the message, normalized to bare email addresses.
Unlike To — whose meaning is provider-specific for historical reasons
(MS Graph populates it from the first reply-to address; Gmail from the raw
To: header) — this is the actual recipient list as received. Optional:
providers that cannot supply it leave it undefined.
All CC recipients of the message, normalized to bare email addresses. Optional: providers that cannot supply it leave it undefined.