If you running Mail server on a machine other than that on which you have installed Primary HC Setup, then you have to install Hosting Controller Secondary setup on the machine where Mail server is running and configure the following settings on both Primary and Secondary HC installations.
Configuration On Primary Machine:
Enable remote Mail:
In Start menu Programs folder, go to NT Web Hosting Controller and click Settings. The Settings utility dialog will appear.
In Settings dialog, click on Servers tab, check the Mail on Remote Server check box and provide the IP of the server where Mail is running in Mail Server IP box.
Click OK to apply the new setting.
Configuration On Secondary Machine:
Enable local Mail:
In Settings dialog, click on Mail tab and check the Enabled check box.