.\" @(#)$Id: mh-mts.rf,v 1.10 1992/05/12 22:23:34 jromine Exp $
mh-mts \- the MH interface to the message transport system

.ti .5i

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MMDF (any release)

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\fIMH\fR can use a wide range of message transport systems to deliver mail.
Although the \fIMH\fR administrator usually doesn't get to choose which MTS
to use (since it's already in place),
this document briefly describes the interfaces.

When communicating with \fISendMail\fR,
\fIMH\fR always uses the SMTP to post mail.
Depending on the \fIMH\fR configuration,
\fISendMail\fR may be invoked directly (via a \fIfork\fR and an \fIexec\fR),
or \fIMH\fR may open a TCP/IP connection to the SMTP server on the localhost.

When communicating with \fIzmailer\fP,
the \fISendMail\fP compatibility program is
required to be installed in /usr/lib.
\fIMH\fP communicates with \fIzmailer\fP
by using the SMTP.
It does this by invoking the \fB/usr/lib/sendmail\fP
compatibility program directly, with the `\-bs' option.

When communicating with \fIMMDF\fR,
normally \fIMH\fR uses the \*(lqmm\(ru\*(rq routines to post mail.
However, depending on the \fIMH\fR configuration,
\fIMH\fR instead may open a TCP/IP connection to the SMTP server on the

When using the stand\-alone system (\fBNOT\fR recommended),
\fIMH\fR delivers local mail itself and queues \fIUUCP\fR and network mail.
The network mail portion will probably have to be modified to reflect the
local host's tastes, since there is no well\-known practice in this area for
all types of UNIX hosts.

If you are running a UNIX system with TCP/IP networking,
then it is felt that the best interface is achieved by using either
\fISendMail\fR or \fIMMDF\fR with the SMTP option.
This gives greater flexibility.
To enable this option you append the /smtp suffix to the mts option in the
\fIMH\fR configuration.
This yields two primary advantages:
you don't have to know where \fIsubmit\fR or \fISendMail\fR live.
This means that \fIMH\fR binaries (e.g., \fIpost\fR\0)
don't have to have this information hard\-coded,
or can run different programs altogether;
second, you can post mail with the server on different systems, so you don't
need either \fIMMDF\fR or \fISendMail\fR on your local host.
Big win in conserving cycles and disk space.
Since \fIMH\fR supports the notion of a server search\-list in this respect,
this approach can be tolerant of faults.
Be sure to set \*(lqservers:\*(rq as described in
mh\-tailor(8) if you use this option.

There are four disadvantages to using the SMTP option:
First, only UNIX systems with TCP/IP are supported.
Second, you need to have an SMTP server running somewhere on any network your
local host can reach.
Third, this bypasses any authentication mechanisms in \fIMMDF\fR
or \fISendMail\fR.
the file \fB/etc/hosts\fR is used for hostname lookups
(although there is an exception file).
In response to these disadvantages though:
First, there's got to be an SMTP server somewhere around if you're in the
Internet or have a local network.
Since the server search\-list is very general,
a wide\-range of options are possible.
SMTP should be fixed to have authentication mechanisms in it, like POP.
\fIMH\fR won't choke on mail to hosts whose official names it can't verify,
it'll just plug along
(and besides
if you enable the BERK or DUMB configuration options,
\fIMH\fR ignores the hosts file altogether).
^@(MHETCPATH)/mtstailor~^tailor file
\fIMMDF\-II: A Technical Review\fR,
Proceedings, Usenix Summer '84 Conference
\fISENDMAIL \-\- An Internetwork Mail Router\fR
mh\-tailor(8), post(8)
The @(MHETCPATH)/mtstailor file ignores the information in the \fIMMDF\-II\fR
tailoring file.
It should not.