Symptoms

When trying to send email, the error "SMTP mail send failure: Verify the SMTP connection strings are correct and that SMTP is working properly. Exception: Failure sending mail." is logged. No emails are sent.
 

Diagnoses

This occurs when the SMTP connection strings are either not setup correctly, or SMTP should not be used.
 

Resolution

Update the K2HostServer.exe.config file to use SmartactionsEWS instead of SmartActionsSMTP.