Under Exchange 2013 Architecture:
“Second, Outlook clients no longer connect to a server FQDN as they have done in all previous versions of Exchange. Outlook uses Autodiscover to create a new connection point comprised of mailbox GUID, @ symbol, and the domain portion of the user’s primary SMTP address. This simple change results in a near elimination of the unwelcome message of “Your administrator has made a change to your mailbox. Please restart.” Only Outlook 2007 and higher versions are supported with Exchange 2013.”