file contains a list of mail addresses or programs
that the user's mail should be redirected to.
file is not present, then no mail forwarding will be done.
Mail may also be forwarded as the standard input to a program
by prefixing the line
with the normal shell pipe symbol (|).
are to be passed to the command, then the entire line
should be enclosed in quotes.
For security reasons, the
file must be owned by the user the mail is being sent to,
or by root, and the user's shell must be listed in
For example, if a
file contained the following lines: