Mattermost

Mattermost is a secure, open-source team chat and collaboration app built for high-compliance work. Organize conversations by channels and threads, share files, and keep projects moving with boards and playbooks. Integrate your DevOps and business tools to automate workflows and speed up incident response. Deploy self-hosted or in the cloud to maintain full data control with enterprise-grade security and compliance. Ideal for IT, DevOps, and business teams needing reliable, searchable communication and high-efficiency, secure collaboration.