Postfix Overview - Goals and Features
   
  The goal of the Postfix project is to implement a viable alternative
  to the UNIX Sendmail program. Specific goals, and the ways that
  Postfix attempts to achieve them are:

* Wide dissemination. Postfix must be adopted by lots of people in
  order to make a significant impact on Internet mail performance and
  security. Therefore the software is given away for free, with no
  strings attached to it.

* Performance. Postfix is up to three times as fast as its nearest
  competitor. A desktop PC running Postfix can receive and deliver a
  million different messages per day. Postfix uses web server tricks
  to reduce process creation overhead and uses other tricks to reduce
  file system overhead, without compromising reliability.

* Compatibility. Postfix is designed to be sendmail-compatible to make
  migration easy. Postfix supports /var/mail, /etc/aliases, NIS, and
  ~/.forward files. However, Postfix also attempts to be easy to
  administer, and therefore it does not use sendmail.cf.

* Safety and robustness. Postfix is designed to behave rationally
  under stress. When the local system runs out of disk space or
  memory, the Postfix software backs off, instead of making the
  problem worse. By design, no Postfix program keeps growing as the
  number of messages etc. increases. Postfix is designed to stay in
  control.

* Flexibility. Postfix is built from over a dozen little programs that
  each perform only one specific task: receive a message via SMTP,
  deliver a message via SMTP, deliver a message locally, rewrite an
  address, and so on. Sites with specific requirements can replace one
  or more little programs by alternative versions.  And it is easy to
  disable functionality, too: firewalls and client workstations don't
  need local delivery at all.

* Security. Postfix uses multiple layers of defense to protect the
  local system against intruders. Almost every Postfix daemon can run
  in a chroot jail with fixed low privileges. There is no direct path
  from the network to the security-sensitive local delivery programs -
  an intruder has to break through several other programs
  first. Postfix does not even trust the contents of its own queue
  files, or the contents of its own IPC messages. Postfix avoids
  placing sender-provided information into shell environment
  variables. Last but not least, no Postfix program is set-uid.

       
Other significant features of interest

* Multiple transports. In the past the author has configured Sendmail
  systems that could relay between Internet, DECnet, X.400 and
  UUCP. Postfix is designed to be flexible enough that it can operate
  in such environments without requiring virtual domain or alias
  kludges. However, the initial release only talks SMTP, and has only
  limited support for UUCP.

* Virtual domains. In the most common case, adding support for a
  virtual domain requires change to only a single Postfix lookup
  table. Other mailers usually need multiple levels of aliasing or
  redirection to achieve the same result.

* UCE control. Postfix can restrict what hosts can relay their mail
  through a Postfix system, and supports restrictions on what mail is
  allowed to come in. Postfix implements the usual suspects:
  blacklists, RBL lookups, HELO/sender DNS lookups. Content filtering
  hasn't been implemented yet.

* Table lookups. Postfix does not yet implement an address rewriting
  language. Instead it makes extensive use of table lookups. Tables
  can be local dbm or db files, or networked NIS or NetInfo
  maps. Adding support for other lookup mechanisms is relatively easy.


Flavors

pcre	Include support for Perl-compatible regular expressions
sasl	Include support for authenticated SMTP using Cyrus SASL v1 (deprecated)
sasl2	Include support for authenticated SMTP using Cyrus SASL v2 (recommended)
tls	Include support for SMTP over SSL/TLS
ldap	Include support for doing table lookups using LDAP
mysql	Include support for doing table lookups using MySQL


WWW: http://www.postfix.org/
WWW: http://www.aet.tu-cottbus.de/personen/jaenicke/pfixtls/

Maintainer: Jakob Schlyter <jakob@openbsd.org>
