Office 365 Mailbox Activity Report
User Signed Into Mailbox
This report shows information about the sign-in events that occurred when the user signed in to a mailbox.
Sent Message Using Send On Behalf Permissions
This report displays the information about the mails which are sent using the Send On Behalf permissions.
Sent Message Using Send As Permissions
This report shows information about the mails which are sent using the Send As permissions.
