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 shows 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.
Created Mailbox item / Updated message
This report shows information about the delegate permissions which are added / removed.
Delegate mailbox permissions Added / Removed
This report shows information about the delegate permissions which are added / removed.
Moved messaged to deleted items folder/ another folder
This report shows information about the mails that are moved to deleted items folder / another folder.
Copied Message to another folder / Deleted message from deleted items folder
This report shows information about the mails that are copied to deleted items folder / another folder.
Modified folder permissions
This report shows information about the folder permissions which are modified.