Google Calendar Interop is an extremely useful utility for organizations that utilize both Calendar in G Suite and Microsoft Exchange Online. It enables the two services to communicate with each other so users can see each other"s calendar across different resources and book meetings accordingly. Now, Google has announced an important configuration change for companies using Calendar Interop.
As we know, Microsoft is deprecating Basic Authentication protocols for Exchange Online in October 2022 and transitioning to Modern Authentication (OAuth). What this means is that Google Workspace customers who configured Interop to use Basic Authentication to establish communication between Google Calendar and Exchange Online services on Microsoft 365 will be cut off too.
As such, Google has recommended that affected customers should upgrade to OAuth 2.0 prior to October 1, 2022. Google Calendar Interop has supported this method of authentication since June 2020.
It is important to note that Basic Authentication in Exchange Online will not stop working for everyone all at once on October 1. Instead, it will be phased out in a staggered manner, but no exemptions will be granted to anyone.
Regardless, it is better to be prepared beforehand instead of waiting for disruptions to happen on October 1. As such, IT admins managing Google Workspace for their organization should refer to step 4 in the guide here to configure the use of OAuth 2.0 in Google Calendar Interop as soon as possible. It is important to note that only customers integrating with Exchange Online are affected, the configuration change is not necessary for on-premises Exchange customers.