+(defun nnmail-purge-split-history (group)
+ "Remove all instances of GROUP from `nnmail-split-history'."
+ (let ((history nnmail-split-history)
+ prev)
+ (while history
+ (setcar history (delete-if (lambda (e) (string= (car e) group))
+ (car history)))
+ (pop history))
+ (setq nnmail-split-history (delq nil nnmail-split-history))))
+