Suppose the following scenario: a small company that has Exchange Online service and a hosting service that use Cpanel platform. After finally configure all DNS records and successfully connect to Exchange Online, randomly users begun to report two issues:
1) Public folder disappears.
2) Outlook Error: "Outlook cannot log on".
How Outlook works with Exchange Service? the response is Autodiscover service. but how Autodiscover service works?
This function has three phases to get all necessary information to connect to the Exchange Server. This phases are:
1) Define the candidate pool.
2) Try Autodiscover endpoints.
3)Try Other Alternatives.
But, what happen if phase 1 & 2 fails?
Obviously, the response is phase 3. In this phase, Autodiscover attempt to use other alternatives in the following order.
1) Get request. That try to get results accessing the path http://autodiscover.domainhost.com/autodiscover/autodiscover.xml.
2) DNS Query. That try to query DNS for SRV records.
Now, go back to the scenario. How to fix it? You need to access your cpanel and locate the Autodiscover folder. You need to deleted and create the SRV record that point to Autodiscover for Exchange Online.