Note This scenario applies only to Microsoft Office 365 customers who have a hybrid deployment of Exchange Online and on-premises Exchange Server.
When you try to use the Microsoft Remote Connectivity Analyzer tool to troubleshoot Microsoft Exchange ActiveSync (EAS) in your organization, you receive the following error message:
ActiveSync URL was in an Invalid format. It should be https://host/Microsoft-Server-ActiveSync. The URL was <Your URL>.
Note When you run the test, an HTTP request is sent to the MobileSync Autodiscover provider on the Client Access server. This request is made to obtain an external URL for ActiveSync devices to use when ActiveSync devices connect to the Exchange server.
This issue occurs if the external URL isn't in the following format:
Note In this URL, the <hostname> placedholder represents the fully qualified domain name (FQDN) of the external Domain Name System (DNS) that ActiveSync devices use to connect to EAS.
To fix this issue, check the setting of the ExternalURL property for the Microsoft-Server-ActiveSync virtual directory on the on-premises Exchange server. To do this, follow these steps:
Open Exchange Management Console (EMC) on the on-premises Exchange server.
Expand Server Configuration, select Client Access, select the appropriate Client Access server, and then click the Exchange Active Sync tab.
Select the Microsoft-Server-ActiveSync virtual directory, and then click Properties.
Make sure that the ExternalURL property uses the following format: