What webmail app do you use? I only know of Squirrel Mail and Round Cube and use the latter currently. Are there other options for webmail interfaces?
Are both of these webmail apps able to be used at DH? Or are these hosted elsewhere?
I don’t think you can install webmail apps on a shared server. That should require root privilege.
However, you may be able to install on PS. It’s better to ask DH support.
And if you are not familiar on how to manage webmail apps, it’s better to use DH’s or Google’s one. They have professionals to manage that.
A while back, I had installed RoundCube for one of my domains. I didn’t need root or any other special privileges. It worked pretty well, but I so rarely use webmail here that I abandoned the idea.