Calendar Interop error messages

Here's how to troubleshoot different error messages you might see when using the Google Calendar Interop troubleshooting tool.


Error message Description Recommended action
Connection error

Google Calendar was not able to connect to the Microsoft Exchange server. A firewall might be blocking access. Or, you entered the wrong host name or port. For example, you might see this error if you failed to connect to

Use the Microsoft Remote Connectivity Analyzer tool to verify if the Exchange server is reachable from the internet.
EWS communication error The Exchange server URL has HTTP rather than HTTPS. HTTP is not a secure protocol. Make sure to specify HTTPS in the Exchange server URL.
EWS response error

Google servers aren’t communicating with Exchange Web Services (EWS), but some other service (for example, a non-Exchange HTTP server).

Common causes of this error include:

  • You entered the wrong URL for the Exchange server.

  • You entered incorrect Exchange credentials.

  • There is a firewall preventing Calendar from connecting to the EWS server. In this case, make sure that the EWS port is accessible from the internet.

In Exchange 2016, to find the correct URL, go to Exchange admin center > servers > virtual directories and then double-click EWS.

Refer to Microsoft Exchange Web Services Connectivity Tests in the Microsoft Remote Connectivity Analyzer tool for more information.

Exchange username is not an
email address

The Exchange username specified in the Admin console is not a valid email address. For example, it might be missing the domain name.

Check the username to ensure it’s 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.

Interop is not configured

No Exchange connection settings were found. Calendar Interop might not be configured in the Google Admin console.

Make sure Calendar Interop is turned on in the Admin console.
Invalid attendee

The user you’re doing an availability lookup for doesn’t exist.

Make sure the user you’re doing the lookup for exists in Microsoft Active Directory.
Malformed Exchange URL

The 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.
SSL error

This message is the result of one of the following errors:

  • The SSL certificate doesn't match the name of the host you’re trying to connect to. You might have entered an IP address instead of a host name. Or, tried to connect using an alias that’s not recognized by the certificate.

  • The SSL certificate is invalid. The certificate might be expired. Or, it might have been issued by 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.
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