As of the release of Outlook 2016, Microsoft has chosen to begin requiring the use of Autodiscover for setting up Outlook clients to communicate with the server. This means that, moving forward, Autodiscover will need to be properly configured.
This page contains some information and some links to other posts I’ve written on the subject of Autodiscover. This page is currently under construction as I write additional posts to assist in configuring and troubleshooting Autodiscover.
The initial configuration of Autodiscover requires that you have a Digital Certificate properly installed on your Exchange Server. If you use a Multi-Role configuration (No longer recommended by MS for Exchange versions after 2010), the Certificate should be installed on the CAS server.
The certificate should have a Common Name that matches the name your users will be using to access Exchange. If you want users to use mail.domain.com to access the Exchange server, make sure that is the Common Name when creating the certificate.
The optimal configuration for Exchange also requires that you include autodiscover.domain.com as a Subject Alternate Name (SAN). You should also make sure that there is also an A or CNAME record in DNS to point users to autodiscover.domain.com. SAN certificates can cost significantly more money than a normal certificate, but there are ways to bypass the need for a SAN certificate (See the next section below for more info).
A Wildcard certificate is usable with Exchange, and can serve as a less expensive way to provide support for a large number of URLs. A Wildcard can also be used on other servers that use the same DNS domain as the Exchange server. However, wildcards are technically not as secure as a SAN cert, since they can be used with any URL in the domain. In addition, they do not support Sub-domains.
The certificate you install on Exchange should also be obtained from a reputable Third Party Certificate Authority. The following Certificate Authorities can generate Certificates that are trusted by the majority of web browsers and operating systems:
Also note, when generating your Certificate Signing Request (CSR), you should generate the CSR with a sufficient bit length. Currently, the recommended minimum for CSR generation is 2048 bits. 1024 and lower bit lengths may not be supported by Certificate Authorities.
Exchange Server Configuration
Autodiscover will determine the settings to apply to client machines by reading the Exchange Server configuration. This means the Exchange Service URLs must be properly configured. If they are not configured to use a name that exists on the Certificate in use, Outlook will generate a Certificate Error.
I will write a post on this subject in the future. For now, you can get this information easily from a Google Search.
There are 2 different URLs Autodiscover will use when searching for configuration information. These URLs are based on the user’s Email Domain (The portion of the email address after the @). For email@example.com, the Email Domain is acbrownit.com. The URLs checked automatically are:
As long as one of the above URLs exists on the Certificate and has an A record or CNAME record in DNS pointing to a CAS server, Autodiscover will work properly. The instructions for this can vary depending on the DNS provider you use.
There are some situations that may cause autodiscover to fail if the above requirements are all met. The following situations require additional setup and configuration.
Domain Joined Computers
Computers that are part of the same Active Directory Domain as the Exchange server will attempt to reach the Active Directory Service Connection Point (SCP) for Autodiscover before attempting to find autodiscover at the normal URLs listed above. In this situation, you will typically need to configure the SCP to point to one of the URLs on your certificate.
Go to this post to find instructions for configuring the SCP:
Single Name Certificates
If you do not want to spend the additional money required to obtain a SAN or Wildcard certificate for Exchange, you can use a Service Locator (SRV) Record in DNS to define the location of autodiscover. A Service Locator Record allows you to define any URL you want for the Autodiscover service, so you can create one to bypass the need for having a SAN or Wildcard certificate.
Go to this post to find instructions for configuring a SRV record: