When you install Microsoft Exchange 2013 you might notice that instead of a nice looking server name of your Exchange server, it now displays a strange looking guid followed by your domain as the servername as soon as you try to resolve your server and mail account name. A sample of this is shown on the screenshot below.
This is by design and actually stands for the GUID of the mailbox you are connecting to followed by the domain hosting the account as you can see by querying for the mailbox ID using PowerShell:
The autodiscover proces takes care of resolving the Exchange server name in combination with your account name to this combination.
Microsoft Exchange 2013 contains several new architectural changes of which this is one of the consequences. Since each Exchange 2013 server now is both a Client Access Server (CAS) and a Mailbox Role server, it is now no longer routing to a specific server but is utilizing autodiscover to connect to any available Microsoft Exchange 2013 server. This allows for easier load balancing and failover protection. TechNet states in this article about this:
The Exchange 2013 architecture provides the following benefits:
Session indifference With Exchange 2010, session
affinity to the Client Access server role was required for several
protocols. In Exchange 2013, the client access and mailbox components
reside on the same Mailbox server. Because the Client Access server
simply proxies all connections for a user to a specific Mailbox server,
no session affinity is required at the Client Access servers. This
allows inbound connections to Client Access servers to be balanced using
techniques provided by load-balancing technology like least connection
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.