For nearly twenty years, Thunderbird has been the open-source alternative for workplaces, universities, and public institutions that are predominantly Outlook-based. And there has always been a clear reason for that status: Microsoft Exchange. Thunderbird lacked native support for Exchange, forcing users to rely on paid add-ons, fragile workarounds, or limited IMAP setups.
That finally changes now.
According to early details shared by BleepingComputer, Thunderbird 145 introduces native Microsoft Exchange support through Exchange Web Services (EWS). This removes the need for extensions like OWL and greatly simplifies switching away from Outlook.
What Native Exchange Support Means in Thunderbird 145
Until this release, Thunderbird users connecting to Exchange had only three clumsy choices—IMAP/POP with reduced features, third-party extensions, or simply giving up and sticking with Outlook.
With Thunderbird 145:
- Exchange accounts can be set up directly from the Account Hub. Enter your work address, authenticate via Microsoft OAuth2, and Thunderbird automatically detects the server and configures EWS.
- All folders sync, including shared mailboxes and custom folder structures. The experience feels complete and smooth.
- Server-side folder management, message flags, attachment handling, and basic search all work as expected.
In short, you don’t lose any core email features.
Current Limitations: Email Only (for Now)
Not everything is included yet. Mozilla notes that EWS support in Thunderbird 145 is limited to mail:
- Calendar and contact sync are not yet available—they’re planned for a future update.
- Microsoft Graph, the modern API Microsoft wants apps to use with Microsoft 365, is also on the roadmap. For now, Thunderbird uses EWS, a technology Microsoft already labels as “legacy.”
Still, for many people, simply having a dependable Exchange email without plug-ins covers most of what they need.
A Direct Challenge to Outlook in Business
This update arrives at a moment when several European public institutions—such as the state of Schleswig-Holstein in Germany—are shifting from Outlook/Exchange to open-source solutions with Thunderbird at the center.
Combined with the growing frustration over Microsoft’s new Outlook, Thunderbird suddenly appears to be a much more serious competitor in corporate environments.
