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.

A long-established low latency voice option whose client is free and whose server can be hosted by the user. Encryption based on AES is on by default, permissions split by server or channel, and clients cover five desktop and mobile systems. The new client is still in testing.

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.

Proton Mail encrypts message bodies on your device, so the provider holds ciphertext it cannot open. Swiss jurisdiction, no phone number required, a usable free tier and password protected mail for outsiders.

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 team voice service that started in 2008 as a tool for group play and grew into a tree of permission-controlled channels. It still prioritises low latency and a fine-grained role system, with screen sharing and file transfer alongside the voice rooms.

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.