mailwrapper(8)

NAME

mailwrapper - invoke appropriate MTA software based on con
figuration 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/sbin/sendmail.
sendmail(8) 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 send
mail(8) helps
in installing alternative MTAs, it essentially makes the
configuration of
the system depend on hard 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 im
plicit configuration information in a read-only /usr.
The mailwrapper utility is designed to replace
/usr/sbin/sendmail and to
invoke an appropriate MTA instead of sendmail(8) based on
configuration
information placed in /etc/mail/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 re
placing
sendmail(8). For example, if the replacement MTA does not
support the -A
option with mailq(1), daily_status_include_submit_mailq
should be turned
off in /etc/periodic.conf.

FILES

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

DIAGNOSTICS

The mailwrapper utility will return an error value and print
a diagnostic
if its configuration file is missing or malformed, or does
not contain a
mapping for the name under which mailwrapper was invoked.

SEE ALSO

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

HISTORY

The mailwrapper utility first appeared in NetBSD 1.4 and
then
FreeBSD 4.0.

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 "be
have differently if invoked with a different name" behavior of things
like mailq(1)
should go away.
BSD December 16, 1998
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