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MAILWRAPPER(8)		  BSD System Manager's Manual		MAILWRAPPER(8)

     mailwrapper -- invoke appropriate MTA software based on configuration

     Special.  See below.

     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, re-
     placement 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(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 configura-
     tion 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 adminis-
     trator 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.

     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.

     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.

     mail(1), mailq(1),	newaliases(1), mailer.conf(5), periodic.conf(5),

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

     Perry E. Metzger <>

     The entire	reason this program exists is a	crock.	Instead, a command for
     how to submit mail	should be standardized,	and all	the "behave differ-
     ently if invoked with a different name" behavior of things	like mailq(1)
     should go away.

BSD			       December	16, 1998			   BSD


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