updateMessage applies selected mutable fields. Recipient, subject, and body
changes are generally draft-only; read state, flags, categories, and importance
also apply to received mail where Microsoft allows them.
Example
automations/update-outlook-draft.automation.ts
Inputs
messageId is required. Optional replacements are to, cc, bcc, subject,
body, bodyType, categories, importance, isRead, and flagStatus
(notFlagged, complete, or flagged). bodyType only matters when replacing
body and defaults to text for that update. Recipient lists replace, rather
than append to, their existing fields. account selects the binding.
Output
Returns Graph’s updated normalizedOutlookMessage. Microsoft rejects fields
that are not writable for the message’s current state.