netbsd man page for mailwrapper

MAILWRAPPER(8)						    BSD System Manager's Manual 					    MAILWRAPPER(8)

NAME
     mailwrapper -- invoke appropriate MTA software based on configuration file

SYNOPSIS
     Special. See below.

DESCRIPTION
     Once upon time, the only Mail Transfer Agent (MTA) software easily available was ``sendmail''.  This famous MTA was written by Eric Allman
     and first appeared in 4.1BSD.  The legacy of this MTA affected most Mail User Agents (MUAs) such as mail(1); the path and calling conventions
     expected by ``sendmail'' were compiled in.

     But times changed.  On a modern NetBSD 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 that may appear in the place of /usr/sbin/sendmail, but still follow the same calling conventions
     as ``sendmail''.

     The ``sendmail'' MTA also typically has aliases named mailq(1) and newaliases(1) 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 replacement programs that plug replace ``sendmail'' helps in installing alternative MTAs, it essentially makes the configura-
     tion 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 mailwrapper program is designed to replace /usr/sbin/sendmail and to invoke an appropriate MTA 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.

EXIT STATUS
     mailwrapper exits 0 on success, and >0 if an error occurs.

FILES
     Configuration for mailwrapper is kept in /etc/mailer.conf.  /usr/sbin/sendmail is typically set up as a symlink to mailwrapper which is not
     usually invoked on its own.

DIAGNOSTICS
     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), newaliases(1), postfix(1), mailer.conf(5)

HISTORY
     The mailwrapper program appeared in NetBSD 1.4.

AUTHORS
     Perry E. Metzger <perry@piermont.com>

BUGS
     The entire reason this program exists is a crock.	Instead, a command for how to submit mail should be standardized, and all the ``behave
     differently if invoked with a different name'' behavior of things like mailq(1) should go away.

BSD
								  April 10, 2010							       BSD