Zimbra

Zimbra is an open-source email and collaboration platform designed for businesses and organizations seeking a customizable and self-hosted solution. It offers a comprehensive suite of features, including email, calendar, contacts, and tasks, making it suitable for teams that require flexibility and control over their data. Zimbra is scalable, accommodating the needs of businesses of all sizes, and provides a wide range of functionalities beyond just email. However, it does require technical expertise for setup and maintenance, and while it may not have as many AI-driven features as some competitors, it remains a solid choice for those prioritizing customization. Additionally, users may find the interface less modern compared to other email clients on the market.