Exchange Server 2013 & 2016 – Allowing host/IP anonymous relaying

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If you have a host or application that is not capable of authenticating via SMTP but need to be able to relay e-mail from the host or application through your Exchange 2013 or 2016 e-mail server you can setup host/ip based relaying.  This allows replaying for the host or app that’s coming from a specific IP address.  To enable this feature you have to setup a ‘Relay’ Receive Connector as follows:

  1. Connect to the Exchange admin center.
  2. Go to Mail Flow > receive connectors.
  3. Click the + symbol to add a new receive connector.
  4. Give the connector a name like “IP_AnonRelayConnector”.
  5. Select Frontend Transport under the Role.
  6. Select Custom under the Type.
  7. Click the Next button.
  8. Accept the default for the Network adapter bindings.
  9. Click the Next button.
  10. Under the Remote network settings, highlight the default entry “0.0.0.0-255.255.255.255” and click the – to delete the entry.
  11. Click the + symbol to add a new IP address.
  12. Enter the IP address of the host or application that you want to allow relaying for.
  13. Click the Save button.
  14. Go into the new receive connector to edit it and select security.
  15. Make sure the following are the only items checked
    1. Transport Layer Security (TLS)
    2. Externally secured (for example, with IPsec)
    3. Exchange servers
    4. Anonymous users
  16. Click the Save button.
  17. Restart the Microsoft Exchange Transport Service (command line “Restart-Service MSExchangeTransport”).
  18. Test that you’re now able to relay through the new connector from the host or application.