How Autodiscover works in Exchange Online, Exchange On-Premise and Hybrid Exchange – Part 1

December 24th, 2018 | Posted by admin in Exchange

Everyone knows how Exchange Autodiscover works, as it is there from Exchange Server 2007. Writing this blog to show how it works for Exchange Online, Exchange On-Premise and Exchange Hybrid environment.

Microsoft Exchange Autodiscover service in Exchange helps the Autodiscover capable outlook clients to configure outlook profile easily by providing minimal input. Users know their user name and password information, by providing those information, other information to configure outlook profile can be retried from Exchange using Autodiscover Service. Autodiscover automatically configures user profile for outlook and mobile devices.

Outlook 2007 and later clients supports Autodiscover to connect Exchange 2007 and above.

How Autodiscover works?

Information that are required to configure the outlook profile will be retrieved from Exchange in a XML format and outlook use that information to connect to different services to function properly.

How Autodiscover works when connecting from Internal network.

Note: To locate Autodiscover service, outlook uses LDAP query to Service Connection Point object first (Internal clients) and if it fails it uses DNS query (external clients).

  1. Once user enters the credential (email address and password, where email address is considered as a user name), outlook authenticated with AD and queries for Service Connection Point objects to find the Autodiscover Service in Client access server to which it has to contact to get the Autodiscover information in xml format.

SCP object will be created when Exchange client access server installed and new SCP will be created when new CAS servers are installed, SCP will be updated with the servicebindinginformation FQDN of client access server name in the form of https://cas01.learnexchangeserver.com/autodiscover/autodiscover.xml and keyword that tells to which site this CAS server belongs.

Once the client authenticated to active directory,

  • The Autodiscover service information will be obtained from SCP object, for any reason it that fails
  • Outlook will try the predefined URL like https://autodiscover.learnexchangeserver.com/autodiscover/autodiscover.xml by using DNS
  • If the above fails, outlook will try the HTTP redirect method, it is same predefined URL, instead of https, http will be used
  • If the above fails, SRV record lookup will be used which is the last lookup method and if that fails outlook auto configuration will fail.
  1. Autodiscover Service in CAS server contacts AD to get the URL and the configured Exchange Services details
  2. Autodiscover Service returns a HTTPS response with XML file that includes connection settings and URLS for available Exchange features
  3. Outlook client uses that information to connect to Exchange.

How Autodiscover works when connecting from Internet.

If the Client Machine is not domain joined, or connecting from Internet.

  1. Outlook first tries to locate the Autodiscover service by looking up the SCP object in Active Directory. Since the client is in internet, it will not be able to contact Active Directory,
  2. Outlook Client will try to locate the Autodiscover service by DNS query.

For DNS query, outlook uses the right side of the email address (domain name), that is, learnexchangeserver.com, and then check the DNS for two predefined URLs. For example

https://learnexchangeserver.com/autodiscover/autodiscover.xml

https://autodiscover.learnexchangeserver.com/autodiscover/autodiscover.xml

Note: Need to create a DNS record in Internet to connect to your Client Access Server to make it work.

  1. Autodiscover Service in CAS server contacts AD to get the URL and the configured Exchange Services details
  2. Autodiscover Service returns a HTTPS response with XML file that includes connection settings and URLS for available Exchange features
  3. Outlook client uses that information to connect to Exchange.

On the next part we will see how the Autodiscover work for Exchange Online / Exchange On-Premise and Exchange Hybrid environment.

You can follow any responses to this entry through the RSS 2.0 You can leave a response, or trackback.

Leave a Reply