http://www.fmi.uni-passau.de/archive/doc/unix/unixhelp/Unixhelp/mail_five.3.2.html (Einblicke ins Internet, 10/1995)The command
reads the mail that is in your system mailbox. This is a file named after your username that is in the directory /usr/spool/mail.
There are other files where your mail can be kept and which you might want to read.