86 lines
4.2 KiB
Plaintext
86 lines
4.2 KiB
Plaintext
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Postfix Overview - Goals and Features
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_________________________________________________________________
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The goal of the Postfix project is to implement a viable alternative
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to the UNIX Sendmail program. Specific goals, and the ways that
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Postfix attempts to achieve them are:
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* Wide dissemination. Postfix must be adopted by lots of people in
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order to make a significant impact on Internet mail performance
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and security. Therefore the software is given away for free, with
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no strings attached to it.
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* Performance. Postfix is up to three times as fast as its nearest
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competitor. A desktop PC running Postfix can receive and deliver a
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million different messages per day. Postfix uses web server tricks
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to reduce process creation overhead and uses other tricks to
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reduce file system overhead, without compromising reliability.
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* Compatibility. Postfix is designed to be sendmail-compatible to
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make migration easy. Postfix supports /var/mail,
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/etc/aliases, NIS, and ~/.forward files. However, Postfix also
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attempts to be easy to administer, and therefore it does not use
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sendmail.cf.
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* Safety and robustness. Postfix is designed to behave rationally
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under stress. When the local system runs out of disk space or
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memory, the Postfix software backs off, instead of making the
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problem worse. By design, no Postfix program keeps growing as the
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number of messages etc. increases. Postfix is designed to stay in
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control.
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* Flexibility. Postfix is built from over a dozen little programs
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that each perform only one specific task: receive a message via
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SMTP, deliver a message via SMTP, deliver a message locally,
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rewrite an address, and so on. Sites with specific requirements
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can replace one or more little programs by alternative versions.
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And it is easy to disable functionality, too: firewalls and client
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workstations don't need local delivery at all.
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* Security. Postfix uses multiple layers of defense to protect the
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local system against intruders. Almost every Postfix daemon can
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run in a chroot jail with fixed low privileges. There is no direct
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path from the network to the security-sensitive local delivery
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programs - an intruder has to break through several other programs
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first. Postfix does not even trust the contents of its own queue
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files, or the contents of its own IPC messages. Postfix avoids
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placing sender-provided information into shell environment
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variables. Last but not least, no Postfix program is set-uid.
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Other significant features of interest
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* Multiple transports. In the past the author has configured
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Sendmail systems that could relay between Internet, DECnet, X.400
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and UUCP. Postfix is designed to be flexible enough that it can
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operate in such environments without requiring virtual domain or
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alias kludges. However, the initial release only talks SMTP, and
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has only limited support for UUCP.
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* Virtual domains. In the most common case, adding support for a
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virtual domain requires change to only a single Postfix lookup
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table. Other mailers usually need multiple levels of aliasing or
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redirection to achieve the same result.
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* UCE control. Postfix can restrict what hosts can relay their
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mail through a Postfix system, and supports restrictions on what
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mail is allowed to come in. Postfix implements the usual suspects:
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blacklists, RBL lookups, HELO/sender DNS lookups. Content
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filtering hasn't been implemented yet.
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* Table lookups. Postfix does not yet implement an address
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rewriting language. Instead it makes extensive use of table
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lookups. Tables can be local dbm or db files, or networked NIS or
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NetInfo maps. Adding support for other lookup mechanisms is
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relatively easy.
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_________________________________________________________________
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For more information, visit http://www.postfix.org/
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And remember, it's spelled P-o-s-t-f-i-x, but it's pronounced "VMailer."
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-d.
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---
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http://www.monkey.org/~dugsong/
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