Roundcube Webmail is a browser-based, multilingual IMAP client with an application-like user interface. It provides the full functionality you expect from an email client, including MIME support, address book, and folder manipulation. High extensibility is granted by the plugin API and the user interface is fully skinnable using XHTML and CSS 2.
OBM is a groupware, email, LDAP, Windows PDC, CRM, and project management application. It is mainly used as a mail server, as an LDAP directory, as a Windows PDC, as a contact and customer database, as a project management tool, or as any combination of these functions. It supports internationalization and themes.
gnokii is a multisystem tool suite for mobile phones. It provides a library to communicate with a phone hiding the communication protocol. The library handles SMS, phonebook, calendar, phone calls, and other mobile phone capabilities. It supports Nokia-FBUS mobiles, AT-capable phones (most of the mobiles), as well as Symbian-based phones.
Fetchmail is a free, 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, and ESMTP ETRN, ODMR, SMTP, LMTP, and local delivery agents.
Ampache is a Web-based audio file manager. It allows you to view, edit, and play your audio files via the Web. It has support for playlists, artist and album views, album art, random play, playback via HTTP with on-the-fly transcoding and downsampling, vote based playback, playback via MPD and Icecast, an integrated Flash player, and per-user themes and song play tracking. You can also link multiple Ampache servers together using XML-RPC. Ampache supports gettext translations and has full translations into many languages.
MIMEDefang is a flexible MIME email scanner designed to do all kinds of email processing, including anti-virus scanning, anti-spam scanning, replacing parts of messages with URLs, adding boilerplate disclaimers, and so on. It can alter or delete various parts of a MIME message according to a Perl-based policy filter. It can also bounce messages with unacceptable attachments and modify SMTP response codes on the fly. It works with the Sendmail 8.11 and newer "Milter" API, which makes it more flexible and efficient than procmail-based approaches.
centericq is a text mode menu- and window-driven IM interface that supports the ICQ2000, Yahoo!, AIM, IRC, MSN, Gadu-Gadu, and Jabber protocols. It allows you to send, receive, and forward messages, URLs, SMSes (both through the ICQ server and email gateways supported by Mirabilis), contacts, and email express messages, and it has many other useful features. An internal RSS reader and a LiveJournal client are also provided.
Gammu (formerly known as MyGnokii2) is a cellular manager for various mobile phones/modems. It supports a wide variety of Nokia, Symbian, and AT devices (Siemens, Alcatel, Falcom, WaveCom, IPAQ, Samsung, SE, and others) over cables, infrared, or BlueTooth. It contains libraries with functions for ringtones, phonebook, SMS, logos, WAP, date/time, alarm, calls, and more (used by external applications like Wammu). It also includes a command line utility that can make many things (including backups) and an SMS gateway with full MySQL and PostgreSQL support from the PHP interface.
Sylpheed is a simple, lightweight but featureful, and easy-to-use email client. It has a well-polished and comfortable user interface. It has many features such as multiple accounts, thread display, MIME, powerful filtering, various search interface, spell checking, and junk mail control. It supports common email protocols such as POP3, IMAP4rev1, SMTP, and security features such as GnuPG and SSL/TLSv1. It is also fully internationalized and multilingualized.
MatrixSSL is an embedded SSL and TLS implementation designed for small footprint devices and applications requiring low overhead per connection. The library is less than 50Kb on disk with cipher suites. It includes client and server support through TLS 1.2, mutual authentication, session resumption, and implementations of RSA, ECC, AES, 3DES, ARC4, SHA2, SHA1, and MD5. The source is well documented and contains portability layers for additional operating systems, cipher suites, and cryptography providers.