You could construct a file with a text editor, save it, and then send it as the body of a message.
To send the ASCII file named a01 to a user named p373 use the command
mail p373 < a01Rather than taking the message from the keyboard, in this case the mail utility takes its input from the file a01, as specified by the Unix redirection sign <. Note that the file comprises the entire message. This procedure does not fill in a subject field for the file. To do that you must use the variant:
mail -s "Assignment 1" p373 < a01The subject field for the generated message is Assignment 1. Please be sure to enclose the text of the subject field with quotes. Note: Not all mail versions understand the -s option.