A communication tool that puts public key cryptography into everyday messaging, with chat and file sharing both encrypted end to end and an optional timer that makes sensitive messages vanish. Clients cover five systems, the code is published under a BSD licence, though the release rhythm has slowed to maintenance.

Chat organised the way mail is organised: every message belongs to a channel and a topic, so hundreds of messages stay readable, replies can arrive days later, and self hosting is free.

With commercial voice services the rooms, the permissions and the data all sit in somebody else's account. Mumble takes the self hosted route: a small server runs Murmur, and a community or a squad has its own voice house with channels, permission tiers and user management under local control.

Jami is an open source, decentralised messenger: no account to create, no central server in the path, and messages plus voice and video calls travel device to device. Free on every major platform, it hands control of a conversation back to the two people having it.

A chat client built on the open Matrix protocol, with end to end encryption, servers you can run yourself and federation between them, and Spaces for organising rooms. The client is free and open source, and the current version is 1.12.28.

An open team communication platform that keeps messages, calls, tickets and a customer service desk in one system running on your own machine. Channels, meetings and an omni-channel inbox are built in, and the latest releases add semantic search and an agent interface.

A mail client that treats mail, calendar and contacts as one workspace: invitations become appointments, birthdays appear in the schedule, encryption is built in rather than bolted on, and the desktop applications are joined by an Android version.