Open Source Alternatives to Zimbra Collaboration

An email and collaboration suite that provides email, calendar, and file management capabilities. The software is designed for enterprises, government institutions, and educational sectors that require data sovereignty and deployment flexibility. It includes an intuitive email interface, real-time chat, and a file management tool called Briefcase for secure server-side storage with granular access controls and version tracking. The platform is built on open standards and can be deployed on-premises, in a private cloud, or in regional data centers to meet specific regulatory and data residency requirements. It supports scalability from 10 users to 10 million users and provides visibility into the email infrastructure through auditable code. This allows organizations to maintain control over where their data resides while eliminating vendor dependency through the use of open interworking standards.

Whether you want to cut software costs or escape vendor lock-in, these open source alternatives to Zimbra Collaboration give you an option you fully own. You can self-host them, so your data stays on infrastructure you control. This page lists 3 open source alternatives to Zimbra Collaboration. The most popular are Stalwart Mail Server, mailcow and WildDuck. Most use the AGPL-3.0 or eupl-1.2 license, and 3 offer an official Docker image.