Neal, we have added some discussion items on our end and will definitely take your feedback in mind for a future release.
Configuring a new set of ports for each domain would be the required configuration here to secure multiple domains. I understand this creates a bit of extra work to manage these ports; in SmarterMail 16 we've added a search feature in the Ports section to allow you to search for the specific port set. By editing the items returned in the search results, you would be able to bind them to the desired IP's.
You may also want to look into unified communication certificate (also known as Multiple Domain SSL Certificates) which would give you the ability to secure multiple host names within a single certificate. This would allow you have a single set of SSL bindings simplifying the management of the certificate within SmarterMail.
Thank you for your feedback. Please let me know if you have any questions or concerns.
Technical Support Specialist / Internal IT