The purpose of the mailbox. Differentiates a mailbox for a single user from a shared mailbox and equipment mailbox in Exchange Online. Possible values are: user, linked, shared, room, equipment, other
Userpurpose property explained
Userpurpose is an exchange property that can tell what a users mailbox is used for.
To allow Bsure Insights to read these values you have to give the managed identity inside the application access to read these settings by adding the following permission MailboxSettings.Read