You know I didn’t even think about that method. It just didn’t dawn on me to hit Roundcube with the server’s name… but it makes a lot of sense in that is how most ISPs do it. They don’t give everyone their own URL for webmail.
Well, one thing is that by doing what I did was quick and simple and makes it a bit more intuitive to the user.
I wrote this to explain how I finally figured out how to add a user: