Mac OS X, which combines a powerful core foundation with a compelling user interface called Aqua. With advanced features and an aesthetically refined use of color, transparency, and animation.
I initially wrote SirAdmin as a diagnostic tool, so that when users reported problems with certain mailboxes, my IT support staff who were not comfortable with the command line interface of cyradm could assign themselves an ACL to view such mailboxes in their own email client in order to quickly diagnose whether the reported problem was server-side or client-side.