Synchronizing User Accounts with Microsoft 365 (Modern Authentication)
https://help.mailstore.com/en/server/Synchronizing_User_Accounts_with_Microsoft_365_(Modern_Authentication)
https://help.mailstore.com/en/server/Office_365_Integration#Accessing_Directory_Service_Integration
If synchronization fails due to:
Requesting Microsoft Graph API token failed: AADSTS70002: Error validating credentials. AADSTS50012: Invalid client secret is provided.
Refer to this link: