message-mark-insert-file
message-mark-insert-file is an interactive compiled Lisp function in `message.el
'.
(message-mark-insert-file FILE &optional VERBATIM)
Insert FILE at point, marking it with enclosing tags.
See `message-mark-insert-begin' and `message-mark-insert-end'.
If VERBATIM, use slrn style verbatim marks ("#v+" and "#v-").