Other than forwarding mail messages over a TCP/IP network,
does not handle mail delivery itself. Instead,
it runs other programs that perform delivery (see
The programs it runs are called
. Information about
which agent performs which kind of delivery is defined in the
The first item to put in your
file is a
definition of the program (delivery agent) that
forwards mail to the hub machine.
That definition provides
with the information
it needs to deliver mail using that delivery agent.
needs to include only
the name and location of that program.
Therefore, in its preliminary form, the definition for the mail delivery program
looks like this:
# This is a comment
V7 # this is another comment
# Delivery agent definition to forward mail to hub
Mhub, P=[IPC], A=IPC $h
This is a minimal (and still useless) configuration file.
Go ahead and add these new lines to
The second line is a configuration command that defines a delivery agent.
It contains three parts, each separated from the others by commas: a
symbolic name and two equates.
that begins the line defines a mail delivery agent.
immediately following is the symbolic
name for the delivery agent. This symbolic name will be
referenced by other parts of the
configuration file when you write them.
equate stands for Path. This says that the full
pathname of the program that is used
to handle the delivery is called
is a special name used internally by
to represent its
to communicate over TCP/IP networks.
It stands for interprocessor communications).
For other mail
delivery agent definitions the name following the
would be the full pathname of a program, such as
equate stands for Argument vector (list). It is used
to specify the command-line arguments that will be given
program when it is run. The zeroth argument
is the name of the program (here
The rest of the arguments, of which there is only one here, the
are the actual
command-line arguments. The
is a macro that contains
the recipient's hostname. We'll describe macros in the next chapter.
equate is traditionally the last item in a delivery
with this command line:
/usr/lib/sendmail -oQ/tmp -Cclient.cf -bp
Note that you need to include
command line to
trying to change to the
(which probably doesn't exist under the current directory).
If you leave out the
exits with this confusing error:
cannot chdir((null)): Bad file number
to use the file
in the current directory as its configuration
file, rather than the system
to print the contents of the
The above command line should produce output like the following:
No local mailer defined
The lack of a
mailer is not important yet.
prints it and stops but otherwise found no errors in our