Autodiscover is the feature that Outlook uses to obtain configuration information for servers to which it connects. In Outlook 2016 with Exchange servers or Office 365 (O365), Autodiscover is considered the single point of truth for configuration information and must be configured correctly for Outlook to be fully functional. The domain's DNS SRV record must point to the correct target for Outlook Anywhere configuration and URL settings.
Autodiscover, Click-to-Run release of Outlook 2016 (Office 365 subscription)
NOTE: The Autodiscover implementation of boxed, retail licenses of Outlook 2016 behave with slight differences. From Mailprotector's Support team experience, the behavior is similar except for checking for Office 365 endpoints before root domain addresses.
Microsoft Support Reference
Detailed information is available on Microsoft's Support website.
Troubleshooting the Autodiscover process may result in unexpected behavior. If that is the case, it is possible the registry settings associated with the Autodiscover key are altered.