Hello, @StefanoB,
Welcome to the Microsoft Q&A platform!
You can sync your on-premises Exchange with Exchange Online using a hybrid deployment. This setup allows you to manage both environments as a single entity. Here are the steps to enable and force the synchronization:
1.Prerequisites: Ensure that all prerequisites are met and that your provisioning agent is up to date before the configuration.
2.Set Up Hybrid Configuration: Use the Hybrid Configuration Wizard (HCW) to configure your hybrid environment. You can download and run HCW from the Exchange Admin Center in your Office 365 portal.
3.Enable Exchange Hybrid Writeback: Sign in to the Microsoft Entra admin center as a Hybrid Administrator and enable Exchange Hybrid Writeback with the help of https://learn.microsoft.com/en-us/entra/identity/hybrid/cloud-sync/exchange-hybrid#how-to-enable.
4.Force Synchronization: Force the synchronization of Active Directory objects with Office 365 using the following PowerShell cmdlet. This command initiates a delta sync, which synchronizes only the changes since the last sync.
Start-ADSyncSyncCycle -PolicyType Delta
5.Provisioning On-Demand: Sign in to the Microsoft Entra admin center, navigate to your configuration, and use the Provision on demand feature by following https://learn.microsoft.com/en-us/entra/identity/hybrid/cloud-sync/exchange-hybrid#provisioning-on-demand.
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Thank you for your support and understanding.
Best Wishes,
Alex Zhang