Software

GPG-enabled mailing list manager with resending-capabilities. ([Source Code](https://0xacab.org/schleuder/schleuder/tree/master))

Mailing list manager. ([Source Code](https://github.com/sympa-community/sympa))

Feed reader for your email accounts. ([Source Code](https://github.com/cypht-org/cypht))

Browser-based IMAP client with an application-like user interface. ([Source Code](https://github.com/roundcube/roundcubemail))

Another browser-based IMAP client. ([Source Code](https://sourceforge.net/p/squirrelmail/code/HEAD/tree/))

Modern IRCv3 server written in Go, combining the features of an ircd, a services framework, and a bouncer. ([Source Code](https://github.com/ergochat/ergo))

Modular IRC server written in C++ for Linux, BSD, Windows, and macOS. ([Source Code](https://github.com/inspircd/inspircd))

Responsive web IRC client with theming support. ([Demo](https://kiwiirc.com/nextclient/), [Source Code](https://github.com/kiwiirc/kiwiirc))

Portable and lightweight Internet Relay Chat server for small or private networks. ([Source Code](https://github.com/ngircd/ngircd))

Distributed IRC client, meaning that one (or multiple) client(s) can attach to and detach from a central core. ([Source Code](https://github.com/quassel/quassel))

IRC without netsplits. Distributed IRC server, based on RobustSession protocol. ([Source Code](https://github.com/robustirc/robustirc))

Web IRC client. ([Demo](https://demo.thelounge.chat/), [Source Code](https://github.com/thelounge/thelounge))

Modular, advanced and highly configurable IRC server written in C for Linux, BSD, Windows, and macOS. ([Source Code](https://github.com/unrealircd/unrealircd))

Fast, light and extensible chat client. ([Source Code](https://github.com/weechat/weechat))

Advanced IRC bouncer. ([Source Code](https://github.com/znc/znc))

Easy to use but advanced IP PBX system, VoIP gateway and conference server. ([Source Code](https://github.com/asterisk/asterisk))

Complete, modular and scalable SIP server, includes a push gateway, to deliver SIP incoming calls or text messages on mobile device platforms where push notifications are required to receive information when the app is not active in the foreground. ([Source Code](https://github.com/BelledonneCommunications/flexisip))

Web-based GUI that controls and manages Asterisk. ([Source Code](https://git.freepbx.org/projects/FREEPBX))

Scalable cross-platform telephony platform. ([Source Code](https://github.com/signalwire/freeswitch))

Web interface for multi-platform voice switch called FreeSWITCH. ([Source Code](https://github.com/fusionpbx/fusionpbx))

Modular SIP server (registrar/proxy/router/etc). ([Source Code](https://github.com/kamailio/kamailio))

SIP proxy/server for voice, video, IM, presence and any other SIP extensions. ([Source Code](https://github.com/OpenSIPS/opensips))

Lightweight SIP proxy, location server, and registrar for a reliable and scalable SIP infrastructure. ([Source Code](https://github.com/fonoster/routr))

VoIP troubleshooting and monitoring platform. ([Demo](https://demo.sip3.io), [Source Code](https://github.com/sip3io/))