You can access our Basic Webmail client (Atmail) by going to:
We're currently beta testing AfterLogic WebMail Pro, which might become our new default WebMail for basic accounts.
Alternatively, we also offers several light-weight open-source webmail clients:
Atmail v5: http://atmail.emailarray.com
You can choose your preferred Default WebMail in Domains > Edit section of the Admin Panel, assuming that you have pointed the webmail CNAME properly.