Hi there- we have an application which sends out email notifications to a third party vendor. The vendor was previously using Exchange Server 2010 and they have recently migrated to Exchange Server 2013. They have also implemented NLB and have two Client Access Servers configured.
Our application has been spitting out "SMTP 5.7.1 Client does not have permissions to send as this sender" errors ever since the vendor has implemented NLB. As our application uses the IP address of the Exchange Server, we have tried specifying the IP address of both the Client Access Servers but that did not help. We then tried specifying the IP address of the NLB which did not make any difference either. The vendor has confirmed that anonymous relay has been enabled on the receive connectors of both the Client Access Servers. I must add that our application sits on the vendor's server and the application and exchange servers are in the same domain. The "Send From" email address is an existing mailbox configured by the vendor.
Telnet from the App server to the NLB on port 25 has gone through without any dramas.
Is there anything else we would need to check to get this working?
Cheers