Mozilla Thunderbird will receive native support for the Microsoft Exchange email protocol in July. Support for the agenda and address book should also be added later. This is the first time that Mozilla has added a new protocol to its email client.
The team behind the open source email client writes that it has started integrating Rust components into the Thunderbird code base . Currently, the mail client consists largely of old C++ code, which, according to the developers, made it impossible to integrate the Microsoft Exchange Web Services API. This should be possible by using the Rust programming language.
The intention is that Exchange support will be added in the next stable release of Thunderbird. It is expected to be released in July. The team writes that adding a new protocol is quite an undertaking, initially only adding support for Exchange emails. The intention is that the calendar and address book will also be supported at a later date.
It was already possible to use Exchange accounts via Thunderbird via a third-party add-on, but support was not yet natively built into the client. By October 1, 2026, Microsoft will discontinue the Exchange Web Services API for Exchange Online and Office 365. This means that in two years' time, Exchange support in Thunderbird will no longer work for Exchange accounts hosted by Microsoft, but only for Exchange servers that organizations manage themselves. It is not clear whether the Thunderbird team will switch to the Graph API before then, which should be possible.