Send desktop notifications for folders other than inbox
E.g. KMail allows user to set up each folder (not just Inbox) such that new messages are "acted upon", meaning that desktop notifications will be shown for them. It is a surprising that expensive enterprise product such as MS Office does not have that feature...
Apostolos Kouloukourgiotis commented
This feature is really important! A lot of users filter to folders for prioritising specific emails. With notifications for folders other than inbox missing, the end user is not notified for high priority emails.