Using mh-e , to make it easier to find the variables you'd need to modify to affect a particular command. However, when customizing your mail environment, first try to change what you want in MH, and only change mh-e if changing MH is not possible. That way you will get the same behavior inside and outside GNU Emacs. Many string or integer variables are easy enough to modify using Emacs Lisp. Printing Your Mail talks more about this variable.
Variables can also hold Boolean values.
In Emacs Lisp, the Boolean values are nil , which means false, and t , which means true. Other variables, such as hooks, involve a little more Emacs Lisp programming expertise. In general, commands in this text refer to Emacs Lisp functions. Programs outside of Emacs are specifically called MH commands, shell commands, or Unix commands. I hope I've included enough examples here to get you well on your way.