Auto discovery in Exchange 2013+ and Office 365

Exchange 2013+ and Office 365 both use the Microsoft Autodiscover service to determine the Client Access Server (CAS) URL associated with a specific email address.

The CAS URL must be determined for each mailbox to subscribe to notifications, which is the default mode of operation for notifications in both Exchange 2013+ and Office 365. The Email Notification module runs auto discovery (the Microsoft Autodiscover service) during the subscription process for an email address. After the subscription process, the URL is cached for the user and mailbox, and then another auto discovery occurs only if the subscription fails. Caching the URL speeds up the subscription process.

If auto discovery is configured correctly in your environment, the process takes only a few seconds to resolve the CAS URL for a specific email address. For more information about the Autodiscover service, see the following Microsoft documentation at http://technet.microsoft.com/en-us/library/bb124251%28v=exchg.150%29.aspx.