SOGo

SOGo is a fully‑featured, open‑source groupware server that exposes mail, calendar, address book and task data through a rich AJAX‑based web UI while simultaneously acting as an interop hub for standard protocols such as CalDAV, CardDAV, GroupDAV and Microsoft ActiveSync. From a developer’s perspective it is an API‑first platform: all user data is exposed via RESTful endpoints and WebDAV interfaces, making it straightforward to build custom clients or integrate with existing infrastructure. The server is designed for high scalability, having been deployed in environments serving thousands of users with minimal performance degradation.

• Core Engine: SOGo is written in C++, leveraging the SOPE (SOGo Object Programming Environment) framework, a lightweight web server abstraction that handles HTTP requests, session management and authentication.
• Database Layer: It supports several back‑ends—PostgreSQL, MySQL/MariaDB, SQLite and Oracle. The data model is exposed through an object‑relational mapping layer that abstracts database differences, allowing developers to target any of the supported engines with minimal code changes.
• Web Interface: The front‑end is built with AJAX, JavaScript, and HTML5. It follows a component‑based architecture where each module (mail, calendar, address book) can be swapped or extended without touching the core.
• Protocol Support: ActiveSync, CalDAV, CardDAV, GroupDAV, IMAP/SMTP are all implemented natively. The ActiveSync implementation is fully compliant with the Microsoft specification, enabling direct Outlook or mobile device sync.

• RESTful Services: /api/v1/... endpoints provide CRUD operations for mail, calendar events, contacts, and tasks.
• WebDAV: Traditional CalDAV/CardDAV/GroupDAV endpoints (/caldav, /carddav) allow full compatibility with any client that understands these standards.
• ActiveSync: A dedicated /sync endpoint handles push/pull synchronization for mobile devices.
• Plugin Architecture: Developers can write SOPE plugins in C++ or embed scripting languages (e.g., JavaScript via SpiderMonkey) to hook into authentication, data filtering or UI customization.
• Webhooks & Callbacks: The server can emit events (e.g., mail received, calendar updated) that external services may subscribe to via HTTP callbacks.

• Self‑Hosting: SOGo runs on any Linux distribution (Debian, Ubuntu, CentOS) or FreeBSD. It requires a web server front‑end (Apache, Nginx, Lighttpd) or can be deployed as a standalone HTTP server via the built‑in SOPE engine.
• Containerization: Official Docker images are available, and the project includes a .devcontainer configuration for VS Code Remote‑Containers. This makes CI/CD pipelines straightforward: spin up a container, run tests against the API, and push to production.
• Scalability: Horizontal scaling is achieved by running multiple SOGo instances behind a load balancer, sharing the same database back‑end. The stateless nature of most API calls means that any instance can serve any request, simplifying autoscaling on Kubernetes or cloud platforms.

• Authentication: LDAP, PAM, OpenID Connect and OAuth2 are supported out of the box. Custom authentication modules can be added as SOPE plugins.
• External Storage: Mail can be stored in IMAP servers or local files; calendars and contacts reside in the chosen database, but can be mirrored to external services via API hooks.
• Custom UI: The web interface is modular; developers can replace or augment widgets, change themes, or inject custom JavaScript modules without recompiling the core.
• Scripting: SOPE’s embedded scripting engine allows runtime evaluation of JavaScript for data transformations, filtering rules, or automated tasks.

• Documentation: The project hosts a comprehensive wiki (https://sogo.nu/support.html) covering architecture, API reference, and migration guides. The source code is well‑structured with inline comments, making it approachable for contributors.
• Community & Support: An active mailing list, IRC channel, and a dedicated GitHub repository foster rapid issue resolution. The project’s open‑source license (GPL/LGPL v2+) encourages community contributions and commercial use.
• Testing: A robust test suite (unit, integration) is available; developers can run it inside the provided dev container to validate changes before merging.

1. Enterprise Groupware – Replace proprietary Microsoft Exchange with a self‑hosted, fully standards‑compliant server that scales to thousands of users.
2. Mobile Sync – Provide iOS/Android devices with native ActiveSync support without a separate Exchange server.
3. Custom Client Development – Build lightweight web or desktop clients that consume SOGo’s RESTful APIs, leveraging the same data store as existing Outlook or mobile clients.
4. Hybrid Deployments – Integrate SOGo into an existing LDAP/Active Directory infrastructure, using it as the central calendar and mail gateway while leaving legacy systems untouched.

• Open Standards First: By exposing CalDAV/CardDAV/ActiveSync, developers avoid vendor lock‑in