In To:/Cc: contacts selection, use the contacts sort order already used in People
My Outlook-on-the-web contacts are displayed in People with surname first and in surname order. This is my preference, and for business users at least this must be the most common usage.
But when I create a new message and select (e.g.) To:, the addresses to select from are displayed with surname first but are in first name order. There is no obvious way to change this and the resulting display is obviously a pointless mess.
Why not either add a 'sort order' option to the To:/Cc: contacts selection or at least use the 'xx first' AND 'xx order' options set for People's display ?