Offer an option to retain the existing theme
I am not really a fan of the default theme presented, sorry. Clearly a lot of work has gone into it but this trend for "flat" and characterless interfaces has resulted in something that to me looks far worse than the current interface offered by Axigen.
Sorry to sound harsh, but I really don't like it. There appears to be no clear delineation between UI sections which means that it seems just too busy to my eyes.
You will be able to retain the existing theme by adding a mapping to the old WebMail pages in WebAdmin → WebMail service → Virtual Hosts.
After the iX release, before you upgrade, you will be able to ask our support team for the old pages.