You need to understand, some people do not like change and for you to do this without asking or telling a paying customer if they would like to change or keep previous version is deplorable business tactics on your part.

In my occupation as Sales Rep, every time the company changed the website ( supposedly for the better, as you say )it made my customers very upset, as they would have to get used to a new ( more modern, as you say ) format....and guess who took the brunt of that frustration ? in some incidences , I lost business because of the change and in my search for other email providers, you might too, as I'm sure other customers may feel the same way..

Thanks for the link to expand my screen and get rid of something I would never use on the right side.... That automatic appearance of the right side of the screen should be an option, not default.

I don't know if you ran a beta version with some of your customers,( especially older customers, as they hate change more than most) but would advise you to do so in the future. It was brought up in a sales meeting to let the Sales force review the changes and make suggestions before releasing to customers, instead of dumping it on them and say " get used to it"... If you would like outside " Boots on the ground " type of consultation, I am available.