where number is the number of the letter to be inserted. For example, to send a letter to another user that includes a copy of letter number 3 from your mailbox list, you would do the following:
On a new line give the command ~m 3 and then press Return.
mailx displays the message, Interpolating: 3 (continue)
You won't see the text of message 3, but the recipient will. You can go on with your letter after (continue), or you can send it as is.
as you're writing a letter. For example, to insert the file outline in the current letter, type: