Free, open-source alternatives to Microsoft Exchange
Microsoft's mail and calendar server. 5 apps you can run yourself instead of Microsoft Exchange, sorted by how well they replace it. Each one is open source, so your data stays with you.
SOGoBest match
SOGo offers multiple ways to access the calendaring and messaging data. CalDAV, CardDAV, GroupDAV, as well as ActiveSync, including native Outlook compatibility and Web interface.
Zimbra Collaboration
Email, calendar, collaboration server with Web interface and lots of integrations.
egroupware
Software suite including calendars, address books, notepad, project management tools, client relationship management tools (CRM), knowledge management tools, a wiki and a CMS.
Stalwart Mail Server
All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.
Group Office
Enterprise CRM and groupware tool. Share projects, calendars, files and e-mail online with co-workers and clients.
Side by side
| App | Stars | License | Activity | Runs on |
|---|---|---|---|---|
| SOGo | 2,171 | LGPL-2.1 | Objective-C | |
| Zimbra Collaboration | - | GPL-2.0, CPAL-1.0 | Java | |
| egroupware | 297 | GPL-2.0 | PHP | |
| Stalwart Mail Server | 15,074 | AGPL-3.0 | Rust, Docker | |
| Group Office | 282 | AGPL-3.0 | PHP |
Why replace Microsoft Exchange?
Microsoft Exchange works, but your data lives in someone else's account, the price can change at any time, and features can disappear. An open-source app you run yourself is yours: you choose where it runs, who can see the data, and when to update.
Questions
What is the best free alternative to Microsoft Exchange?
SOGo is the closest open-source replacement for Microsoft Exchange in our list. Zimbra Collaboration and egroupware are worth a look too, depending on what you need.
Can I self-host an alternative to Microsoft Exchange?
Yes. All 5 apps on this page are open source and can run on your own server, usually with Docker, or on a managed host that installs them for you.