Mattermost

Deploy Mattermost on Out Plane — a self-hosted team communication platform and open-source Slack alternative. Mattermost provides channels, direct messaging, file sharing, threaded conversations, and full-text search. The platform integrates with DevOps tools through incoming and outgoing webhooks, slash commands, and bot accounts.

Mattermost supports LDAP, SAML, and Active Directory authentication for enterprise environments. It is GDPR and HIPAA compliant out of the box, making it suitable for organizations with strict data residency and compliance requirements. Self-hosting on Out Plane gives you full control over message data, file attachments, and user management.

Ideal for development teams, regulated industries, government agencies, and any organization that needs private, self-hosted team communication with enterprise authentication and compliance certifications.