mail-complete
mail-complete is an interactive autoloaded compiled Lisp function in `mailalias.el
'.
(mail-complete ARG)
This function is obsolete since 24.1;
use `mail-completion-at-point-function' instead.
Perform completion on header field or word preceding point.
Completable headers are according to `mail-complete-alist'. If none matches
current header, calls `mail-complete-function' and passes prefix ARG if any.