XEmacs is a full fledged programming language with a mail reader, news reader, info browser, web browser, calendar, specialized editor for more programming languages and other formats than most people encounter in a lifetime, and much more.

After starting it up peruse the Help menu and read more on its origins and what it can do.

You will need one of xemacs21-mule, xemacs21-nomule, or xemacs21-mule-canna-wnn to actually run xemacs.