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How Autodiscover Works




One of the improvements in Exchange 2019 is that that the client configuration became more easier. This is caused because of several improvements in Autodiscover.

The clients that connect via EWS usually are connected to the EWS Endpoint using Autodiscover. It is known that Autodiscover provides also information for other protocol connections also and it support also multiforest configurations.

When Exchange server is installed a virtual directory called Autodiscover  is created. After the appropriate URL are configured and stored in Active Directory the Client Access services that run on the Mailbox server provide authentication services and proxy services for both internal and external client connection.That results that Outlook clients can then connect to Exchange using only the user name and password.

Autodiscover and Active Directory

As said previously the creation of the Autodiscover virtual directory allows Outlook to automatically discover the necessary Exchange mailbox settings saving the users from having to write down and remember server names, ports, protocols, databases, etc. The user can simply provide a username and password and the rest is carried by Outlook.

During the virtual directory creation an  SCP object is also created in Active Directory. That SCP object stores the authoritative URLs for the Autodiscover service and provides them to domain-joined computers. The SCP object points to the Exchange server and provides additional Autodiscover information to clients trying to connect to Exchange.

The SCP object locates the Autodiscover server or endpoint that’s appropriate for the user trying to connect. It provides an easy way for domain-joined mail clients to look up Autodiscover servers.

There are two types of SCP objects for the Autodiscover service that Exchange publishes. SCP pointers and SCP URLs.

SCP pointers contain information that points to specific LDAP servers that are then used to locate Autodiscover SCP objects in the user’s Active Directory domain. SCP URLs contain Autodiscover URLs for Autodiscover endpoints.

The Autodiscover service URL  will be either of the values below:

The URL used will depend on whether the Autodiscover service is configured on a separate site or not.

Autodiscover in DNS

Exchange Server 2019 reduces the number of required namespaces since it does not require RPC Client Access namespaces. The Client Access services now proxy connection requests to whatever Mailbox server is hosting the active Mailbox database for the mailbox being connected to. A new feature in Exchange 2019 is the ability of a  a Mailbox server to proxy a session to another mailbox server in a different Active Directory site thus eliminating the need for  failback namespaces in DAG activation situations.

Outlook and Autodiscover

If Autodiscover is properly configured, Outlook clients can authenticate to Active Directory with just a user’s credentials. It will automatically search for the Autodiscover SCP objects for the domain. Once it finds the Autodiscover service, the Outlook client will connect to the Client Access services on the first Mailbox server it finds. Outlook will then collect profile information in XML format. This information is required to connect to the mailbox.

Autodiscover can use one of four methods to configure an Outlook client:

The first two methods above are typical for smaller organizations with a single SMTP namespace. The second two are typical in multiple-SMTP namespace scenarios.

Outlook uses the Autodiscover service to locate a new connection point. Autodiscover returns the following information to the Outlook client:

  • User display name
  • Internal and external connection settings
  • Mailbox server hosting the active copy of the user’s mailbox
  • URLs for various Outlook features (OAB, OWA, etc.)
  • Outlook Anywhere server settings

If the Exchange information for a user changes, the Outlook client will use the Autodiscover service to automatically reconfigure the user’s profile. This commonly occurs when a mailbox is moved. When this happens, Outlook contacts the Autodiscover service and automatically updates the user’s profile with the new mailbox location so that it can connect.

Autodiscover and certificates

When Exchange is installed, the installation process creates a self-signed certificate that’s signed by the Exchange server itself. This certificate is automatically installed on the server. However it is recommended that you use public certificate from a trusted third party.

You can use the Microsoft Remote Connectivity Analyzer tool to confirm that the Autodiscover service in Exchange 2019 is accessible and functioning as expected. To test Autodiscover with the tool, launch the tool and select the Outlook Connectivity test. The tool will then attempt to connect to Exchange, using Autodiscover. If it fails, there is likely an issue with the external URLs configured in Exchange. Reading the results provided by the tool should reveal clues regarding why connectivity failed.



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