Postfix (software)
Postfix is a free software / open source mail transfer agent (MTA), a computer program for the routing and delivery of email. It is intended as a fast, easy-to-administer, and secure alternative to the widely-used Sendmail MTA.
Postfix is the default MTA for a number of Unix(-like) operating systems.
It is released under the IBM Public License 1.0 which is a free software licence, but is incompatible with the GPL.
Postfix's source code is often used as a famous example of good programming practice.
Formerly known as VMailer and IBM Secure Mailer, it was originally written by Wietse Venema during a stay at the IBM Thomas J. Watson Research Center, and continues to be actively developed today. Postfix was first released in mid-1999.
Features
- Transport Layer Security (TLS)
- delegation of SMTP policies to an external process (this allows Greylisting) and advanced content filtering.
- different databases for maps: Berkeley DB, CDB, DBM, LDAP, MySQL and PostgreSQL.
- mbox-style mailboxes, Maildir-style mailboxes, and virtual domains.
- address rewriting (envelope and header), VERP, SMTP-AUTH via SASL, and more.
- Milter [1] support compatible with Sendmail milters.
- using Policyd-weight, can check e-mail headers against various DNSBLs and for RFC compliance, and reject near-certain spam ahead of receiving the body of the messages, lessening server load.
- can be compiled on AIX, BSD, HP-UX, IRIX, Linux, Mac OS X, Solaris, Tru64 UNIX and, generally speaking, on every Unix-like OS that ships with a C compiler, standard POSIX development libraries and all the libraries required for handling BSD sockets.
One of the strengths of Postfix is its resilience against buffer overflows. Another one is its handling of large amounts of e-mail. Postfix is built as a cooperating network of different daemons. Each daemon fulfills a single task using minimum privileges. In this way, if a daemon is compromised, the impact remains limited to that daemon and cannot spread throughout the entire system. There is only one process with root privileges (master), and a few (local, virtual, pipe) that actually write to disk or invoke external programs. Most daemons can be easily chrooted.
Structure
See Postfix Architecture Overview
Base configuration
The main.cf file stores site specific Postfix configuration parameters while master.cf defines daemon processes. The Postfix Basic Configuration tutorial covers the core settings that each site needs to consider.
Configuration settings for a few common environments are discussed in Postfix Standard Configuration Examples.
Address rewriting and mail routing are covered in Postfix Address Rewriting. The full documentation collection is at Postfix Documentation
References
- Kyle D. Dent (2003). Postfix: The Definitive Guide. O'Reilly Media. ISBN 0-596-00212-2.
- Ralf Hildebrandt and Patrick Koetter (2005). The book of Postfix : state-of-the-art message transport. No Starch Press. ISBN 1-59327-001-1.
See also
External links
- Official website
- Postfix Discussion (mailing list archive)
- http://www.postfixwiki.org/
- http://serverkit.org/modules/postfix-policy A high performance Postfix policy delegation server
- http://www.360is.com/06-postfix.htm Postfix introduction and analysis for secure environments