1 MAILWRAPPER(1M)              Maintenance Commands              MAILWRAPPER(1M)
   2 
   3 NAME
   4      mailwrapper - invoke appropriate MTA software based on configuration file
   5 
   6 SYNOPSIS
   7      Special.  See below.
   8 
   9 DESCRIPTION
  10      At one time, the only Mail Transfer Agent (MTA) software easily available
  11      was sendmail(1M).  As a result of this, most Mail User Agents (MUAs) such
  12      as mail(1) had the path and calling conventions expected by sendmail(1M)
  13      compiled in.
  14 
  15      Times have changed, however.  On a modern UNIX system, the administrator
  16      may wish to use one of several available MTAs.
  17 
  18      It would be difficult to modify all MUA software typically available on a
  19      system, so most of the authors of alternative MTAs have written their
  20      front end message submission programs so that they use the same calling
  21      conventions as sendmail(1M) and may be put into place instead of
  22      sendmail(1M) in /usr/lib/sendmail.
  23 
  24      sendmail(1M) also typically has aliases named mailq(1) and newaliases(1M)
  25      linked to it.  The program knows to behave differently when its argv[0]
  26      is "mailq" or "newaliases" and behaves appropriately.  Typically,
  27      replacement MTAs provide similar functionality, either through a program
  28      that also switches behavior based on calling name, or through a set of
  29      programs that provide similar functionality.
  30 
  31      Although having drop-in replacements for sendmail(1M) helps in installing
  32      alternative MTAs, it essentially makes the configuration of the system
  33      depend on hand installing new programs in /usr.  This leads to
  34      configuration problems for many administrators, since they may wish to
  35      install a new MTA without altering the system provided /usr.  (This may
  36      be, for example, to avoid having upgrade problems when a new version of
  37      the system is installed over the old.)  They may also have a shared /usr
  38      among several machines, and may wish to avoid placing implicit
  39      configuration information in a read-only /usr.
  40 
  41      The mailwrapper utility is designed to replace /usr/lib/sendmail and to
  42      invoke an appropriate MTA instead of sendmail(1M) based on configuration
  43      information placed in /etc/mailer.conf.  This permits the administrator
  44      to configure which MTA is to be invoked on the system at run time.
  45 
  46      Other configuration files may need to be altered when replacing
  47      sendmail(1M).
  48 
  49 EXIT STATUS
  50      The mailwrapper utility exits 0 on success, and >0      if an error occurs.
  51 
  52 DIAGNOSTICS
  53      The mailwrapper will print a diagnostic if its configuration file is
  54      missing or malformed, or does not contain a mapping for the name under
  55      which it was invoked.
  56 
  57 SEE ALSO
  58      mail(1), mailq(1), newaliases(1M), sendmail(1M), mailer.conf(4)
  59 
  60 illumos                         August 20, 2019                        illumos