Exchange 2013 SP1's most significant new feature is adding MAPI over HTTP support.

Traditionally Outlook clients connect to Exchange via RPC over HTTP, a very old technology originally designed to work on small networks, as opposed to over the Internet as it is today!

Well, now that's changed with Exchange 2013 SP1!

You still have to enable it before Outlook 2013 SP1 can use the protocol by running this from EMS:

Set-OrganizationConfig -MapiHttpEnabled $True

Once that has been done, your Outlook client will be prompted to restart to update your MAPI profile.