Hi @Oussama,
Please follow these steps:
1.point the MX record of this domain in public DNS to your Exchange server
2.set this domain to be an internal relay domain in Exchange server
For more detailed information please refer to this link: Relay domains
3.create a send connector to relay messages to recipients hosted in Google Workspace
For the steps please refer to this link: Create a Send connector to route outbound mail through a smart host
In this case we need to configure Google Workspace as the smart host.
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