Postfix Overview - Introduction - SCN Research
Postfix Overview - Introduction - SCN Research
Postfix Overview - Introduction - SCN Research
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<strong>Postfix</strong> Anatomy - Delivering Mail<br />
parallel delivery to the same user is usually limited.<br />
Page 2 of 2<br />
Together with the sendmail mail posting agent, the local delivery agent implements the familiar Sendmail<br />
user interface.<br />
The local delivery agent has hooks for alternative forms of local delivery: you can configure it to deliver<br />
to mailbox files in user home directories, and you can even configure it to delegate mailbox delivery to an<br />
external command such as the popular procmail program.<br />
• The virtual delivery agent is a very much stripped down version of the local delivery agent that delivers to<br />
mailboxes only. This is the most secure <strong>Postfix</strong> delivery agent, because it does not aliases expansions and<br />
no .forward file expansions.<br />
This delivery agent can deliver mail for multiple domains, which makes it especially suitable for hosting<br />
lots of small domains on a single machine.<br />
• The SMTP client looks up a list of mail exchangers for the destination host, sorts the list by preference,<br />
and tries each address in turn until it finds a server that responds. On a busy <strong>Postfix</strong> system you will see<br />
several SMTP client processes running in parallel.<br />
• The LMTP client speaks a protocol similar to SMTP. The client can connect to local or remote mailbox<br />
servers such as Cyrus. All the queue management is done by <strong>Postfix</strong>. The advantage of this setup is that<br />
one <strong>Postfix</strong> machine can feed multiple mailbox servers over LMTP. The opposite is true as well: one<br />
mailbox server can be fed over LMTP by multiple <strong>Postfix</strong> machines.<br />
• The pipe mailer is the outbound interface to other mail transports (the sendmail program is the inbound<br />
interface). The <strong>Postfix</strong> mail system comes with examples for delivery via the UUCP protocol. At the time<br />
of writing, this venerable protocol is still widely used. By default, <strong>Postfix</strong> understands bang path style<br />
addresses.<br />
Up one level | Receiving Mail | Delivering Mail | Behind the Scenes | Command-line Utilities<br />
http://www.porcupine.org/postfix-mirror/delivering.html<br />
6/26/01
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