Microsoft Exchange Server Alternatives for Online

Kolab Now is a comprehensive, secure, and privacy-focused web-based email and groupware suite. Built entirely on free and open-source software, it offers a full range of collaborative tools including email, calendar, contacts, and document management, prioritizing user data ownership and security.

Kolab Community is a comprehensive, free, and open-source groupware suite designed for collaborative work. It provides integrated email, calendar, contacts, and tasks functionalities, empowering individuals and teams to communicate and manage their data efficiently and with a strong focus on data privacy.

SOGo is a powerful open-source groupware server designed for scalability and simplicity. It provides a comprehensive suite of collaborative features including webmail, calendaring, contact management, and task management, with strong support for standard protocols like CalDAV and CardDAV.

Zimbra Collaboration Suite is a comprehensive open source email and collaboration platform designed for businesses. It provides a secure and feature-rich environment for email, calendaring, contacts, tasks, and file sharing, supporting on-premises and cloud deployments.

Kopano is a versatile open-source groupware suite offering email, calendaring, contacts, and online collaboration tools for businesses and organizations. It provides flexible deployment options, including on-premises and hosted solutions, with strong focus on data privacy and security.

Zarafa is an open-source groupware and email server platform, providing powerful collaborative features similar to Microsoft Exchange but with flexibility and cost advantages. It offers email, calendaring, contacts, and task management.

OX Open-Xchange is a comprehensive web-based suite designed for communication, collaboration, and office productivity, offering features like email, calendaring, task management, and document sharing, seamlessly integrating across devices.