Exchange Autodiscover service

Exchange Autodiscover is a web service that helps Microsoft Exchange administrators configure user profile settings for clients running Outlook 2007, Outlook 2010, or Outlook 2013 and  mobile phones running Windows Mobile 6.1 or later. 

Introduced in Exchange Server 2007, the primary purpose of the Exchange Autodiscover service is to establish initial connections to Exchange user mailboxes. Once that connection has been made, it also helps Outlook access Exchange Server features such as the offline address book and unified messaging.