Adrian Aichner wrote: Opens /usr/local/lib/xemacs-21.5-b3/lisp/simple.elc . I unzipped and opened simple.el instead. No match for edebug-defun. I suppose I need another package - edebug looks promising... <installing...> OK, it seems to do something, but what exactly... I do break into the compose-mail function, but the debugger interface doesn't really look much like MS Visual Studio... :-) Ahh, I can single-step with a space... compose-mail starts like this: (interactive (list nil nil nil current-prefix-arg)) (let ((function (get mail-user-agent 'composefunc))) (funcall function to subject other-headers continue switch-function yank-action send-actions))) I can step as far as the first closing brace on the last line; then I get "Symbol's function definition is void: nil" - which the value of the function variable really is... Back to the assignment - function is the 'composefunc property of the mail-user-agent (right?), and mail-user-agent is... 'vm-user-agent I think I'm going to pause here... What next? Bye Vasek