MAILWRAPPER(8) Maintenance Commands and 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)

illumos August 7, 2006 illumos