Outlook and other Office-related clients can use the Autodiscover process to automatically locate services in Microsoft 365. For an organization to use Autodiscover in this manner, it must first configure the appropriate DNS records on the publicly available DNS servers on the Internet.
- In organizations where the internal DNS namespace, such as adatum.local, is different from the Internet DNS namespace, such as adatum.com, the internal DNS servers forward internal client queries to Internet DNS servers.
- In organizations that use split-brain DNS, where internal and Internet DNS namespaces are the same, such as adatum.com, both the internal and Internet DNS servers should be configured to resolve the Autodiscover records in Microsoft 365.
The following table identifies the Autodiscover records that Outlook clients need to connect to Exchange Online in Microsoft 365.
| DNS record |
Purpose |
Value to use |
CNAME
(Exchange Online) |
The Autodiscover service configures Outlook for users. |
Alias: Autodiscover
Target: autodiscover.outlook.com |
CNAME
(Exchange federation) |
The Autodiscover service configures Outlook for users in Exchange federation scenarios. This record is optional, but required when deploying Exchange in a hybrid configuration with Microsoft 365. |
Alias: For example, Autodiscover.service.adatum.com
Target: autodiscover.outlook.com |
The following graphic shows the domain suffix of a user's email address is resolved against DNS. Redirection to Exchange Online occurs next, which then delivers the correct Autodiscover.xml file back to the Outlook client. This file contains all the configuration information.
The Microsoft 365 portal provides the administrator who's doing the initial Microsoft 365 configuration with all the DNS records that are required for proper name resolution. For some DNS providers such as GoDaddy, Microsoft 365 can automatically create all necessary records.
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