It would be nice to have a property or a function to retrieve the mailbox folder of the selected message in Outlook directly using office-js.
In fact, no property or function described here allows us to find out this info : https://learn.microsoft.com/en-us/javascript/api/requirement-sets/outlook/preview-requirement-set/office.context.mailbox.item?view=common-js-preview
Can you add this information in Office.context.mailbox.item (MessageRead) please ?