Mattermost is a flexible, open source messaging platform that enables secure team collaboration

Highlights:

• Achieve peak productivity - empower DevOps to build the best workflows for your company, ship software faster, and collaborate confidently
• Protect your data - maintain full ownership and control of company IP and customer data behind your own firewall or VPN
• Avoid costly catastrophes - safeguard against major security incidents, vendor lock-in, and resource-draining technical debt

Features:

• Communicate seamlessly
• Organized conversations in teams and channels
• Fully searchable message history
• 1-on-1 and group messaging
• Voice, video, and screen sharing
• File, image, and link sharing
• Emoji and rich Markdown formatting
• Multi-language support
• Focus on what’s most important
• Custom desktop, email, and mobile notifications
• Do not disturb mode
• Favorite channels
• Keyword mention alerts
• Accelerate workflows with integrated tools
• Incoming and outgoing webhooks
• Custom slash commands
• Plugins and extensions
• Bots and developer toolkit
• Robust API library
• OAuth 2.0 applications
• Zapier app with more than 700 integrations
• Administer with full control over your data
• eDiscovery and compliance reporting
• Data retention policies
• Custom terms of service
• AD/LDAP authentication and sync
• Enforced multi-factor authentication
• SAML 2.0 single sign-on
• Command line and database management tools
• Performance and system monitoring