December 2003
Beginner
278 pages
10h 47m
English
Content preview from Postfix: The Definitive GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Mail Delivery
Postfix uses the concept of address classes when determining
which destinations to accept for delivery and how the delivery takes
place. The main address classes are local , virtual alias,
virtual mailbox, and relay. Destination addresses that do not fall
into one of these classes are delivered over the network by the SMTP
client (assuming it was received by an authorized client). Depending on
the address class, the queue manager calls the appropriate delivery
agent to handle the message.
Local Delivery
The local delivery agent
handles mail for users with a shell account on the system where
Postfix is running. Domain names for local delivery are listed in the
mydestination parameter. Messages sent to a user at any of the
mydestination domains are delivered
to the individual shell account for the user. In the simple case, the
local delivery agent deposits an email message into the local message
store. It also checks aliases and users’ .forward
files to see if local messages should be delivered elsewhere. See
Chapter 7 for more information on
local delivery.
When a message is to be forwarded elsewhere, it is resubmitted to Postfix for delivery to the new address. If there are temporary problems delivering the message, the delivery agent notifies the queue manager to mark the message for a future delivery attempt and store it in the deferred queue. Permanent problems cause the queue manager to bounce the message back to the original sender.
Virtual Alias Messages ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.