MAILWRAPPER(8) FreeBSD System Manager's Manual MAILWRAPPER(8)
NAME
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 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(8) 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 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 implicit
configuration information in a read-only /usr.
The mailwrapper program is designed to replace /usr/sbin/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.
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 invoke smtpd(8) if its configuration file is missing.
It will return an error value and print a diagnostic if its configuration
file is malformed, or does not contain a mapping for the name under which
mailwrapper was invoked.
SEE ALSO
mail(1), mailer.conf(5), mailq(8), newaliases(8), sendmail(8), smtpd(8)
AUTHORS
Perry E. Metzger <
[email protected]>
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(8) should go away.
FreeBSD 14.1-RELEASE-p8 December 14, 2015 FreeBSD 14.1-RELEASE-p8