Why can't the webmail be access via a mobile device?
Accessing the webmail URL via a mobile device presents the login screen, then just a blank blue screen. This applies on both an Android phone and an IPAD.
I would say, sure you can use the mobile APP, but that is also broken. It is often in a disconnected state and you are forced to log out and log in.
I don't think these are news to you. I have seen something similar in the comments before. But another new release and this is still broken.