mh-mts - the nmh interface to the message transport system
Zmailer
MMDF (any release)
nmh can use a wide range of message transport systems to deliver mail. Although the nmh 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 SendMail, nmh always uses the SMTP to post mail. Depending on the nmh configuration, SendMail may be invoked directly (via a fork and an exec), or nmh may open a TCP/IP connection to the SMTP server on the localhost.
When communicating with zmailer, the SendMail compatibility program is required to be installed in /usr/lib. nmh communicates with zmailer by using the SMTP. It does this by invoking the /usr/lib/sendmail compatibility program directly, with the `-bs' option.
When communicating with MMDF, normally nmh uses the ``mm_'' routines to post mail. However, depending on the nmh configuration, nmh instead may open a TCP/IP connection to the SMTP server on the localhost.
If you are running a UNIX system with TCP/IP networking, then it is felt that the best interface is achieved by using either SendMail or MMDF with the SMTP option. This gives greater flexibility. To enable this option you append the /smtp suffix to the mts option in the nmh configuration. This yields two primary advantages: First, you don't have to know where submit or SendMail live. This means that nmh binaries (e.g., post ) don't have to have this information hard-coded, or can run different programs altogether; and, second, you can post mail with the server on different systems, so you don't need either MMDF or SendMail on your local host. Big win in conserving cycles and disk space. Since nmh supports the notion of a server search-list in this respect, this approach can be tolerant of faults. Be sure to set ``servers:'' 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 MMDF
or SendMail. Fourth, the file /etc/hosts 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. Second, SMTP should be fixed to have authentication
mechanisms in it, like POP. Third, nmh 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 DUMB configuration options, nmh
ignores the hosts file altogether).
^/etc/nmh/mts.conf~^nmh mts configuration file
None
MMDF-II: A Technical Review,
Proceedings, Usenix Summer '84 Conference
SENDMAIL -- An Internetwork Mail Router
mh-tailor(8), post(8)
None
None
The /etc/nmh/mts.conf file ignores the information in the MMDF-II
tailoring file.
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