When Inbound SMTP Authentication is enabled with "SMTPAllowConnectionsAnonymous=1" and "SMTPVerifyAuthenticatedSender=1" it permits relay for authenticated users only when they use their actual Internet address mentioned in Person Document to send message.
However, If there is an requirement that connecting 3rd party application is generating an email using from address which is not available in Domino directory the message is failed / rejected with following error message.
SMTP Server: Messages rejected. Authenticated user UserName/OU/Domain from host 10.0.1.1 sending mail from Test.User@example.com failed to match directory address Test.User@example.com
554 Sender address not allowed for this authenticated session.
The requirement is to have option / configuration setting to exclude a particular connecting IP address so that the email sender from is not verified by SMTPVerifyAuthenticatedSender=1