Cloud App Security no longer supports automatic and manual provisioning of the Delegate Account for Exchange Online. If you are using a Delegate Account, Cloud App Security allows you to migrate to a modern authentication-based Authorized Account.
Trend Micro strongly recommends that you complete the migration before October 1, 2022. This is because Microsoft will start retiring Basic Authentication for EWS in Exchange Online on this date. As a result, Cloud App Security cannot use the Delegate Account to connect to your Exchange Online service through EWS and implement protection.
During migration, Cloud App Security provisions an Authorized Account and obtains an access token to gain limited access to protected Exchange Online mailboxes.
Before migration to use token-based authentication is successful, Cloud App Security continues to protect your Exchange Online service by using the current basic authentication.