Processing incoming mail

MMDF receives incoming mail from each channel's input program. How MMDF handles incoming mail is illustrated in Figure 4-2, ``Incoming mail''.

Figure 4-2 Incoming mail

Each message is delivered using this procedure:

1. The submit program determines the destination of the message and then designates the channel to use to deliver the mail.

2. MMDF selects a channel:

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     Mail destined for the local machine goes to the local channel.

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     When the machine is local, but the user is not, mail goes to badusers.

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     If mail requires further processing to determine the destination, the message goes to the badhosts channel.

   • If the message is destined for another machine, such as when the local machine is acting as a gateway between networks, MMDF selects another network channel, such as UUCP.

3. The submit program puts the message in the appropriate channel queue.

4. The deliver program transfers the mail from each queue to the appropriate channel.

5. The message is delivered to the user.