Kolab is described as 'Provides a FOSS communication & collaboration solution that can be completely self-hosted. Take back control of your data and access it via the webinterface, or existing mobile & desktop clients' and is a Calendar app in the office & productivity category. There are more than 50 alternatives to Kolab for a variety of platforms, including Web-based, Linux, Android, Windows and Self-Hosted apps. The best Kolab alternative is Microsoft 365 Copilot, which is free. Other great apps like Kolab are Google Calendar, Fossify Calendar, Google Workspace and Roundcube.
The OX App Suite by Open-Xchange is web-based platform offering a suite of apps like an email client, calendar, contacts magement, cloud storage with synchronization and productivity apps for word processing, spreadsheets and presentations.
Germany
EU
Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more. With the most innovative web application available today, Zimbra boosts the productivity of users on any desktop and dramatically reduces TCO compared to legacy platform vendors.
United States
Kopano puts an email, video meetings, calendaring, and file sharing solution within one single interface.
NetherlandsEU
This app is tailored for families, couples, friends, and groups, providing end-to-end encryption for secure data, seamless calendar creation, syncing, private chats, and widgets for easy access, ensuring you never miss an event.
United Kingdom
grommunio (formerly known as grammm) efficiently combines all requirements of modern, digital communication and collaboration.
GermanyEU
All-in-one European business email and collaboration platform — email, chat, video conferencing, and office suite in one app. Cloud or self-hosted.
CzechiaEU
NexMail is an open-source, modern webmail client designed for self-hosted email servers. Enjoy a clean, intuitive interface with powerful features for managing your emails efficiently.
Pakistan
Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows.
Australia
OBM is a free messaging and collaboration platform useful for just a couple to many thousands of users with strong support for mobile devices.
Web-based team collaboration suite combining email client, calendar, contact and task tools, CRM, project and file management, file sharing, trouble tickets, Rocket.Chat chat, and Collabora online editing. Offers open source, self-hosted, and SaaS options.
GermanyEU
