Free Load balancer trying to authenticate to exchange server


On my Exchange 2016 server I am getting an error:

Inbound authentication failed with error LogonDenied for Receive connector Default Frontend xxxEXCH01. The authentication mechanism is Ntlm. The source IP address of the client who tried to authenticate to Microsoft Exchange is [].

This IP is the load balancer, but I am not sure why it is trying to authenticate


( possibly Exchange 2016 SMTP with STARTTLS virtual service)

or how to change the username if authentication is needed.

Thanks in advance!



1 comment

Tony Vaughan

this could be that a client is trying to authenticate but the LoadMaster is NATing the connection
by default the Loadmaster will NAT traffic to the real server,

if you make the service transparent do you still see the LoadMaster IP in the error message?

please see this link for more details on transparency & SMTP