If you are sending mail from within mail command mode, you can enclose the contents of any message sent to you by using ~m or ~M commands. Typing ~m alone will enclose the contents of the current message, typing ~m 12 will enclose the contents of message #12 and so on.
The ~m uses retained and ignored lists when enclosing headers, the ~M encloses all header fields.
In both cases, the contents of indentprefix
mail variable is
prepended to each line enclosed.