If you've not already submitted a support ticket, please provide us with more details so the community here can help you better. I'm sure you must be getting an error somewhere. Provide us with an error message or some better details so we have a starting point. I have 4 servers here and rarely ever have an email issue related to KH as a whole. Any email issues that I have is either someone failing their logins to the point the server blocks them or blacklisting.