Managing mail with MMDF

About mail channels

A channel permits a machine to exchange data using a single type of network communications protocol. It handles the mail transport protocol so that neither the operating system nor the rest of the MMDF system has to know about the intricacies of a particular mail transport protocol. Channels act not only as protocol handlers, but in some cases actually initiate the communications to the network or to another machine as needed. They also may convert address or message formats as necessary.

For information about the channel programs themselves, see ``Channel programs''.

Common channels include:

badhosts

Called when a specified machine in a mail address is unknown to the local machine to forward the message to a smart host. See ``Routing mail for unrecognized hosts''. The use of ``bad'' is really a misnomer; any mail addressed to an unknown machine is sent on this channel. badhosts uses a different channel, such as uucp or smtp, to perform the actual mail forwarding.

badusers

Called when mail is addressed to an unknown user name to forward messages to a smart host. See ``Routing mail for unrecognized users''. Like badhosts, badusers uses a different channel, such as uucp or smtp, to perform the actual mail forwarding.

list

Called to remail messages. This channel simply invokes submit and feeds the addresses and text back into the MMDF mail system. This is often used to avoid long address validation or to force the validation to occur in the background for very large mailing lists. This also ensures that MMDF sends any problem reports to the list maintainer.

local

Called to deliver mail to mailboxes and processes on the local machine.

micnet

Called to deliver or accept mail from a Micnet network connection.

smtp

Called to deliver or accept mail from a TCP/IP network connection. The SMTP channel transfers messages by establishing a TCP/IP connection to a remote machine, and using the Simple Mail Transfer Protocol (SMTP) to send one or more mail messages. The Internet Protocol (IP) allows many local- or wide-area networks to be interconnected transparently. This permits the MMDF SMTP channel to exchange messages with any machine on any network to which it is connected. For example, if your machine connects to the Internet, you can exchange messages directly with any machine in the world that is also connected to the Internet.

uucp

Called to direct mail to UUCP delivery to another machine, or to accept mail from a UUCP connection from another machine. Incoming mail is converted into the format specified by the Internet technical bulletin, RFC 822, available from the InterNIC Registration Services, or InterNIC. See ``Registering domain names''.

Outgoing mail on the UUCP channel includes a ``From '' line and the mail path arguments are separated by UUCP exclamation point characters (!).

For more information about UUCP, see ``How UUCP works'' and ``Configuring UUCP''.

delay

When you use MMDF in conjunction with the domain name server system, this channel is called to queue messages that temporarily fail address verification because of unavailability of a name server. The MMDF Configuration Manager configures this channel automatically.