MAILWRAPPER(8)          FreeBSD 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 FreeBSD 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 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 mailwrapper program is designed to replace /usr/sbin/sendmail and to
     invoke an appropriate MTA based on configuration information placed in
     ${LOCALBASE}/etc/mail/mailer.conf falling back on /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 replacing
     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
     ${LOCALBASE}/etc/mail/mailer.conf or /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.

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

DIAGNOSTICS
     The 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
     dma(8), mail(1), mailq(1), newaliases(1), mailer.conf(5),
     periodic.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 "behave
     differently if invoked with a different name" behavior of things like
     mailq(1) should go away.

FreeBSD 13.1-RELEASE-p6        October 29, 2014        FreeBSD 13.1-RELEASE-p6