MAILWRAPPER(8) Maintenance Procedures MAILWRAPPER(8)

NAME

/usr/lib/mailwrapper - invoke appropriate MTA software based on
configuration file

SYNOPSIS

Special. See below.

DESCRIPTION

At one time, the only Mail Transfer Agent (MTA) software easily available
was sendmail(8). As a result of this, most Mail User Agents (MUAs) such as
mail(1) had the path and calling conventions expected by sendmail(8)
compiled in.

Times have changed, however. On a modern UNIX system, the administrator
may wish to use one of several available MTAs.

It would be difficult to modify all MUA software typically available on a
system, so most of the authors of alternative MTAs have written their front
end message submission programs so that they use the same calling
conventions as sendmail(8) and may be put into place instead of sendmail(8)
in /usr/lib/sendmail.

sendmail(8) also typically has aliases named mailq(1) and newaliases(8)
linked to it. The program knows to behave differently when its argv[0] is
"mailq" or "newaliases" and behaves appropriately. Typically, replacement
MTAs provide similar functionality, either through a program that also
switches behavior based on calling name, or through a set of programs that
provide similar functionality.

Although having drop-in replacements for sendmail(8) helps in installing
alternative MTAs, it essentially makes the configuration of the system
depend on hand installing new programs in /usr. This leads to
configuration problems for many administrators, since they may wish to
install a new MTA without altering the system provided /usr. (This may be,
for example, to avoid having upgrade problems when a new version of the
system is installed over the old.) They may also have a shared /usr among
several machines, and may wish to avoid placing implicit configuration
information in a read-only /usr.

The /usr/lib/mailwrapper utility is designed to replace /usr/lib/sendmail
and to invoke an appropriate MTA instead of sendmail(8) based on
configuration information placed in /etc/mailer.conf. This permits the
administrator to configure which MTA is to be invoked on the system at run
time.

Other configuration files may need to be altered when replacing
sendmail(8).

EXIT STATUS

The /usr/lib/mailwrapper utility exits 0 on success, and >0 if an error
occurs.

DIAGNOSTICS

The /usr/lib/mailwrapper will print a diagnostic if its configuration file
is missing or malformed, or does not contain a mapping for the name under
which it was invoked.

SEE ALSO

mail(1), mailq(1), mailer.conf(5), newaliases(8), sendmail(8)

OmniOS August 7, 2006 OmniOS