In this KB https://doc.sophos.com/central/Customer/help/en-us/ManageYourProducts/EmailSecurity/SophosGateway/ExternalServices/ConfigureGoogle/index.html#create-an-inbound-gateway-in-google-workspace
To configure this setting, do as follows:
- Sign in to your Google Admin Console.
- Navigate to Apps > Google Workspace > Gmail > Advanced settings.
This no longer exists in Google Workspaces. it is now
AppsGoogle WorkspaceGmailSpam, Phishing and Malware.