Thunderbird delivers. Enjoy safe, fast, and easy email, with intelligent spam filters, quick message search, and customizable views. Brought to you by Mozilla, Thunderbird makes email better.
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Postfix is Wietse Venema's mailer that started life as an alternative to the widely-used Sendmail program. Postfix attempts to be fast, easy to administer, and secure, while at the same time being sendmail compatible enough to not upset existing users. Thus, the outside has a sendmail-ish flavor, but the inside is completely different.
SpamAssassin is a spam filter that can be used on a wide variety of email systems including procmail, sendmail, Postfix, qmail, and many others.
Mutt is a small but very powerful text-based mail client for Unix operating systems.
Though written from scratch, Mutt's initial interface was based largely on the ELM mail client. To a large extent, Mutt is still very ELM-like in presentation of information in menus (and in fact, ELM users will find it quite painless to switch as the default key bindings are identical). As development progressed, features found in other popular clients such as PINE and MUSH have been added, the result bei...
Clam AntiVirus (ClamAV) is an anti-virus toolkit for Unix. The main purpose of this software is the integration with mail servers (attachment scanning). The package provides a flexible and scalable multi-threaded daemon, a commandline scanner, and a tool for automatic updating via Internet. The programs are based on a shared library distributed with the Clam AntiVirus package, which you can use in your own software.
Evolution provides integrated mail, addressbook and calendaring functionality to users of the GNOME desktop.
KMail is the email component of Kontact, the integrated personal information manager of KDE.
GNU Mailman is software to help manage email discussion lists and e-newsletters. Its integrated Web interface provides easy-to-use access for list members and list administrators. Mailman supports built-in archiving, automatic bounce processing, content filtering, digest delivery, spam filters, topics, Usenet gateways, and more. It is fully internationalized, and supports digests and email commands. It runs on any Linux or Unix-like operating system and is compatible with most email and Web serv...
Dovecot is an open source IMAP and POP3 server for Linux/UNIX-like systems, written with security primarily in mind.
RoundCube Webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an e-mail client, including MIME support, address book, folder manipulation, message searching and spell checking. RoundCube Webmail is written in PHP and requires a MySQL or Postgres database. The user interface is fully skinnable using XHTML and CSS 2.
SquirrelMail is a standards-based Webmail package. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages are rendered in pure HTML 4.0 for maximum compatibility across browsers. It has very few requirements, and is very easy to configure and install. It has all the functionality you would want from an email client, including strong MIME support, address books, and folder manipulation.
Exim is a message transfer agent (MTA) developed for Unix systems connected to the Internet. It is similar to Smail 3, but expands on Smail features.
RT is an enterprise-grade ticketing system which enables a group of people to intelligently and efficiently manage tasks, issues, and requests submitted by a community of users.
The RT platform has been under development since 1996, and is used by systems administrators, customer support staffs, IT managers, developers and marketing departments at thousands of sites around the world.
Written in object-oriented Perl, RT is a high-level, portable, platform independent system that eases...
Fetchmail is a full-featured, robust, well-documented remote-mail retrieval and forwarding utility intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections). It supports every remote-mail protocol now in use on the Internet: POP2, POP3, RPOP, APOP, KPOP, all flavors of IMAP, ETRN, and ODMR. It can even support IPv6 and IPSEC.
Fetchmail retrieves mail from remote mail servers and forwards it via SMTP, so it can then be read by normal mail user agents such as mutt, el...
Gnus is a mail- and news- reader that is incorporated into GNU Emacs. Gnus is independently developed, and is frequently merged into GNU Emacs.
Claws Mail is a GTK+ based, lightweight, and fast email client. Almost all commands are accessible with the keyboard. It also has many features such as multiple accounts, POP3/SMTP/IMAP/NNTP support, OpenSSL, GnuPG, and LDAP support, a plugin system, spell checking, filtering, Actions, spam and virus filters, an address book, internationalization, and much more.
ohloh does not support CVS branches, the summary given below is incorrect!!
Beagle is a desktop-independent service for indexing and searching
your data. The Beagle daemon transparently monitors your data and updates the index to reflect any changes. On an inotify-enabled system, these updates (e.g. new files, emails, chat) happen more-or-less in real time. Beagle supports many different file formats and can index files/email/browsing history/chat logs/RSS feeds etc.
Sendmail is a remarkably flexible program, supporting many kinds of mail transfer and delivery including the overwhelmingly popular SMTP.
Liferay Portal is the world's leading enterprise open source portal framework, offering integrated Web publishing and content management, an enterprise service bus and service-oriented architecture, and compatibility with all major IT infrastructures.
SeaMonkey is all-in-one internet application suite. It consist of web-browser, e-mail and newsgroup client, IRC client and HTML editor.