Having worked with several organizations on responsive websites (my own not included at this point, but purely due to time-constraints and commitments to business and home projects), the conversation of an existing site, especially one with customizable interfaces and features, is not as simple as modifying some CSS code to change color, or telling the code that pictures and images can now be made resizable. Delving into the SmarterMail code, this task appears to be significantly more daunting than an average, or "normal" website.
Being one of those who voted this up, I can also see where this would put SmarterMail at the top of the branding game, too. Now that we are both allowed to use, and can, without violation of copyright contract, make CSS changes to SmarterMail code for branding purposes, I would think this idea needs to be put in front of the development and management team at SmarterMail so that it can be properly vetted in a manner which will continue to bring the benefits of SmarterMail to customers and not just throw a responsive version out to the world.
Remember, sudden major changes bring incredible support headaches for all involved. Given some of the major companies running SmarterMail, this could become both a logistics, and technical, nightmare as a responsive version is pushed.
While I understand the frustration, I also believe we should all err on the side of good planning and programming.
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting