mh-mts - the nmh interface to the message transport system

SendMail

Zmailer

MMDF (any release)

stand-alone

THIS IS OUT OF DATE AND NEEDS REWORKING.

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., post0) 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.