Symptoms

Client event notifications were not being sent.
 

Diagnoses

While there was no immediate error in either the Workspace or the HostServer logging one did finally turn up after launching K2 in console mode and starting a Client event:

The SMTP server requires a secure connection or the client was not authenticated. The server response was 5.7.1 Client was not authenticated.
 

Resolution

This required an anonymous relay for the SMTP server. One was created. It was also prudent to check the configuration to ensure that both exchange and the SMTP portions of the configuration had been done appropriately. After ensuring the configuration were solid and verifying in the K2HostServer.exe.config file that enableListners was set to true and the system self node had a valid account to work with the notifications started coming through as we would expect.