Open Source Comms

HexChat is an IRC client based on XChat for Linux , but unlike XChat it’s completely free for both Windows and Unix-like systems.
HexChat was originally called XChat-WDK which in turn was a successor of freakschat.

Features

Easy to use and customizable interface
Cross-platform on Windows, OS X, and Unix-like OSes
Highly scriptable with Python and Perl
Translated in multiple languages
Fully open source and actively developed
Multi-network with auto-connect, join, and identify
Spellcheck, Proxies, SASL, DCC support and more

Mastodon is a Free and Open Source federated social network, made with a focus on personal interaction.

Matrix defines a set of open APIs for decentralised communication, suitable for securely publishing, persisting and subscribing to data over a global open federation of servers with no single point of control. Uses include Instant Messaging (IM), Voice over IP (VoIP) signalling, Internet of Things (IoT) communication, and bridging together existing communication silos - providing the basis of a new open real-time communication ecosystem.

Free email application that’s easy to set up and customize - and it’s loaded with great features!.