mail, rmail-reads mail or sends mail to users

mail , rmail ”reads mail or sends mail to users

 Sending mail    mail [ tw ] [ m message_type ] recipient...    rmail [ tw ] [ m message_type ] recipient... Reading mail    mail [ ehpPqr ] [ f filename ] Forwarding mail    mail F recipient... Debugging    mail [ x debug_level ] [ other_mail_options ] recipient...    mail [ T mailsurr_file ] recipient... 

A recipient is usually a username recognized by login . When recipients are named, mail assumes a message is being sent. It reads from the standard input up to an end-of-file (Ctrl-D), or if reading from a terminal, until it reads a line consisting of just a period. When either of those indicators is received, mail adds the letter to the mailfile for each recipient.