Google advises users that an upgrade to OAuth 2.0 is required in order to continue using Google Workspace Calendar (Calendar Interop) with Microsoft Exchange Online from October 1, 2022. The background is that Microsoft is removing Basic Authentication from Exchange Online.
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Google has already announced support for OAuth2.0 in 2020. This should ensure that Google Workspace Calendar (Calendar Interop) will continue to be available in Exchange Online even after Basic Authentication is disabled. After all, Microsoft has announced that it will begin removing basic authentication in Exchange Online for Exchange Web Services on October 1, 2022.
Google Workspace customers who use Calendar Interop with Basic Authentication in Microsoft Office 365 to enable collaboration between Microsoft Exchange and Google Calendar will then run into a problem – the integration will no longer work. To continue using Calendar Interop, users must upgrade to OAuth 2.0 authentication before October 1, 2022.
OAuth 2.0 in Calendar Interop, Source: Google
Otherwise, problems will occur if Basic Authentication is turned off for the account in Exchange Online. Google has described the details in this document. (via)
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