Turnkey Linux - Redmine

When using confconsole and the Mail Relay setup option, I'm unable to enter an internal mail relay using the custom option.  I enter the internal IP, leave the port as 25 and the username and password blank because this relay doesn't require authentication.  I receive:

Could not connect with supplied parameters.  Please check config and try again.

This mail relay is working without issue for other servers using null username and password.  I'm not familiar enough with postfix to know how to work beyond what may be a limitation of confconsole's mail relay setup.  I would be grateful for suggestions.