mail-recover
mail-recover is an interactive compiled Lisp function in `sendmail.el
'.
(mail-recover)
Recover interrupted mail composition from auto-save files.
If the mail buffer has a current valid auto-save file,
the command recovers that file. Otherwise, it displays a
buffer showing the existing auto-saved draft messages;
you can move to one of them and type C-c C-c to recover that one.