|Error message||Details & troubleshooting|
|Connection error||Google Calendar can't connect to the Exchange server. A firewall might be blocking access. Or, you entered the wrong host name or port.
To verify if the Exchange server is reachable from the internet, use Microsoft Remote Connectivity Analyzer.
|Exchange Web Services (EWS) communication error||The Exchange server URL is using HTTP rather than HTTPS. HTTP is not a secure protocol.
Specify HTTPS in the Exchange server URL.
|EWS response error||Google servers aren't communicating with EWS but are connecting to another service (for example, a non-Exchange HTTP server).
Common causes of this error include:
To find the correct URL for the Exchange server, in Exchange 2016, go to Exchange admin centerserversvirtual directoriesdouble-click EWS.
For more information, refer to Synchronization, Notification, Availability, and Automatic Replies in Microsoft Remote Connectivity Analyzer.
|Exchange username is not an email address||The Exchange username specified in the Google Admin console isn't a valid email address. For example, it might be missing the domain name.
Verify that the Exchange role accounts use the correct email address.
|Host not found||The DNS name is incorrect or misspelled. Or, there's no DNS record for the specified host name.
Make sure the Exchange URL in the Admin console is correct. For details, go to Step 5: Set up the Admin console.
|Interop is not set up||No Exchange connection settings were found. Calendar Interop might not be set up in the Google Admin console.
Make sure Calendar Interop is turned on in the Admin console. For details, go to Step 5: Set up the Admin console.
|Invalid attendee||The user you're doing an availability lookup for doesn't exist. Verify the user exists in Microsoft Active Directory.|
|Malformed Exchange URL||The Google Admin console doesn't recognize the Exchange URL. It might be in the wrong format.
Check the settings in the Admin console and make sure the correct URL is entered. For details, go to Step 5: Set up the Admin console.
|SSL error||The SSL certificate doesn't match the name of the host you're trying to connect to or it's invalid:
You might have entered an IP address instead of a host name. Or, the host tried to connect using an alias that's not recognized by the certificate. If the certificate is invalid, it might be expired. Alternatively, it's from an untrusted root Certificate Authority.
Make sure the SSL certificate on the Exchange server is valid and matches the name of the host you’re trying to connect to.
|Error code & name||Details & troubleshooting|
|400 Bad Request||
|401 Unauthorized||Possible causes of this error are:
Check you correctly followed the steps in 2. Allow Calendar users to see Exchange availability and retry.
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