.\"	$OpenBSD: mailwrapper.8,v 1.10 2009/02/07 16:58:23 martynas Exp $
.\"	$NetBSD: mailwrapper.8,v 1.11 2002/02/08 01:38:50 ross Exp $
.\" $FreeBSD: releng/9.1/usr.sbin/mailwrapper/mailwrapper.8 205938 2010-03-30 21:54:25Z delphij $
.\"
.\" Copyright (c) 1998
.\" 	Perry E. Metzger.  All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\"    must display the following acknowledgment:
.\"	This product includes software developed for the NetBSD Project
.\"	by Perry E. Metzger.
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.\"    derived from this software without specific prior written permission.
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.Dd August 7, 2006
.Dt MAILWRAPPER 8
.Os
.Sh NAME
.Nm \fB/usr/lib/mailwrapper\fR
.Nd invoke appropriate MTA software based on configuration file
.Sh SYNOPSIS
Special.
See below.
.Sh DESCRIPTION
At one time, the only Mail Transfer Agent (MTA) software easily available
was
.Xr sendmail 8 .
As a result of this, most Mail User Agents (MUAs) such as
.Xr mail 1
had the path and calling conventions expected by
.Xr sendmail 8
compiled in.
.Pp
Times have changed, however.
On a modern
.Ux
system, the administrator may wish to use one of several
available MTAs.
.Pp
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
.Xr sendmail 8
and may be put into place instead of
.Xr sendmail 8
in
.Pa /usr/lib/sendmail .
.Pp
.Xr sendmail 8
also typically has aliases named
.Xr mailq 1
and
.Xr newaliases 8
linked to it.
The program knows to behave differently when its
.Va argv[0]
is
.Dq mailq
or
.Dq 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.
.Pp
Although having drop-in replacements for
.Xr sendmail 8
helps in installing alternative MTAs, it essentially makes the
configuration of the system depend on hand installing new programs in
.Pa /usr .
This leads to configuration problems for many administrators, since
they may wish to install a new MTA without altering the system
provided
.Pa /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
.Pa /usr
among several
machines, and may wish to avoid placing implicit configuration
information in a read-only
.Pa /usr .
.Pp
The
.Nm
utility is designed to replace
.Pa /usr/lib/sendmail
and to invoke an appropriate MTA instead of
.Xr sendmail 8
based on configuration information placed in
.Pa /etc/mailer.conf .
This permits the administrator to configure which MTA is to be invoked on
the system at run time.
.Pp
Other configuration files may need to be altered when replacing
.Xr sendmail 8 .
.Sh EXIT STATUS
.Ex -std
.Sh DIAGNOSTICS
The
.Nm
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.
.Sh SEE ALSO
.Xr mail 1 ,
.Xr mailq 1 ,
.Xr mailer.conf 5 ,
.Xr newaliases 8 ,
.Xr sendmail 8