qpsmtpd is an SMTP daemon written in Perl. It was originally designed to be a drop-in replacement for qmail-smtpd, the SMTP component of qmail, and it is now also compatible with Postfix, Exim, sendmail and virtually any software that "speaks SMTP". It has a flexible plugin system, making it easy to interoperate with other pieces in a mail system.
Its main purpose is to allow mail administrators to perform more advanced spam filtering than is possible with other SMTP daemons. As one example of dozens, the earlytalker plugin blocks many viruses and mass mailers based on their characteristic violation of basic protocol, even before they start sending mail data.
The program's main author is Ask Bjørn Hansen. It is licensed under the MIT License.
Exim is a mail transfer agent (MTA) used on Unix-like operating systems. Exim is free software distributed under the terms of the GNU General Public License, and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail.
qmail is a mail transfer agent (MTA) that runs on Unix. It was written, starting December 1995, by Daniel J. Bernstein as a more secure replacement for the popular Sendmail program. Originally license-free software, qmail's source code was later dedicated in the public domain by the author.
A tarpit is a service on a computer system that purposely delays incoming connections. The technique was developed as a defense against a computer worm, and the idea is that network abuses such as spamming or broad scanning are less effective, and therefore less attractive, if they take too long. The concept is analogous with a tar pit, in which animals can get bogged down and slowly sink under the surface, like in a swamp.
Apache SpamAssassin is a computer program used for e-mail spam filtering. It uses a variety of spam-detection techniques, including DNS and fuzzy checksum techniques, Bayesian filtering, external programs, blacklists and online databases. It is released under the Apache License 2.0 and is a part of the Apache Foundation since 2004.
Various anti-spam techniques are used to prevent email spam.
Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail.
Email filtering is the processing of email to organize it according to specified criteria. The term can apply to the intervention of human intelligence, but most often refers to the automatic processing of messages at an SMTP server, possibly applying anti-spam techniques. Filtering can be applied to incoming emails as well as to outgoing ones.
The following tables compare general and technical information for a number of wiki software packages.
Mercury Mail Transport System is a standards-compliant mail server developed by David Harris, who also develops the Pegasus Mail client.
Akismet is a spam filtering service that filters spam from comments, trackbacks, and contact form messages. The filter works by combining information about spam captured on all participating sites, and then using those spam rules to block future spam. Akismet is offered by Automattic, the company behind WordPress.com.
The Courier Mail Server is a mail transfer agent (MTA) server that provides SMTP, IMAP, POP3, SMAP, webmail, and mailing list services with individual components. It is best known for its IMAP server component.
hMailServer is a free email server for Windows created by Martin Knafve. It runs as a Windows service and includes administration tools for management and backup. It has support for IMAP, POP3, and SMTP email protocols. It can use external database engines such as MySQL, MS SQL or PostgreSQL, or an internal MS SQL Compact Edition engine to store configuration and index data. The actual email messages are stored on disk in a raw MIME format. It has active support and development forums.
Backscatter is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.
People tend to be much less bothered by spam slipping through filters into their mail box, than having desired e-mail ("ham") blocked. Trying to balance false negatives vs false positives is critical for a successful anti-spam system. As servers are not able to block all spam there are some tools for individual users to help control over this balance.
Amavis is an open-source content filter for electronic mail, implementing mail message transfer, decoding, some processing and checking, and interfacing with external content filters to provide protection against spam and viruses and other malware. It can be considered an interface between a mailer and one or more content filters.
Haraka is an open source SMTP server. Its architecture is plugin-oriented and event-driven. The server and its plugins are written in JavaScript using the Node.js framework.
PHPMailer is a code library to send (transport) emails safely and easily via PHP code from a web server.
Halon is a commercial scriptable SMTP server. It's available for Linux as well as a software distribution based on FreeBSD.
MailEnable is a Windows-based, commercial email server distributed by MailEnable Pty. Ltd, an Australian-based software company which was established in 2002.
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