The "Enable Outbound Relaying" feature must be active, and specific tenant domains must be explicitly listed in the Proofpoint administrative interface to permit the relay sync. Troubleshooting and Resolution Steps 1. Validate Relay Permissions
If the outbound connector in Microsoft 365 is not updated with current Proofpoint IP ranges, the handshake required for secure address synchronization may fail. proofpoint microsoft o365 relay addresses download failure
Ensure the domain is correctly set to "Relay" rather than just "Inbound" in the Proofpoint console. Navigate to > Account Management > Domains . Verify the domain purpose is set to Relay . Confirm the switch for Enable Outbound Relaying is green. 2. Update Microsoft 365 Connectors The "Enable Outbound Relaying" feature must be active,