Microsoft Outlook is not available as a self-hosted solution but there are some alternatives for power users and business that want to host a solution on-premise. The best Self-Hosted alternative is Mailpile, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Microsoft Outlook and five of them are available as a self-hosted solution so hopefully you can find a suitable replacement. Other interesting Self-Hosted alternatives to Microsoft Outlook are Nextcloud Mail, Open365, Nylas Mail Lives and Orbit Communicator.
Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features. The development of Mailpile is funded by a large community of backers and all code related to the project is and will be released under an OSI approved Free Software license.
The open source cloud with LibreOffice online - LibreOffice online + Seafile + KDE. Improve your productivity and communicate better with your team members. The world is moving forward. Welcome to the open source cloud!.
Nylas Mail Lives is a fork of Nylas Mail that fixes many longstanding issues, improves the client experience, and is committed to publish new releases.
Orbit Communicator is a client server application that's designed to be deployed locally on your desktop machine. It currently provides an integrated email / calendaring experience based on external IMAP mail sources.
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