Thunderbird Desktop has released native support for the Microsoft Graph API, giving users of Microsoft 365 hosted email accounts a path forward as Microsoft phases out Exchange Web Services (EWS) support later this year. The new protocol support is available in the Release channel starting with version 154, while the current Extended Support Release, version 153, supports EWS but not Graph.
Microsoft announced earlier this year that it will begin a phased shutdown of EWS on Microsoft 365 and Exchange Online starting in October 2026, with a goal of complete shutdown in 2027. Users currently connecting to Microsoft 365 or Exchange Online accounts via Thunderbird's EWS support will need to switch to the new Microsoft Graph API support to keep using Thunderbird beyond those dates.
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The transition requires manual effort: Thunderbird does not support migrating accounts between protocols. Users with an existing EWS-connected Microsoft 365 account must first delete that account in Thunderbird's account settings, a step that does not affect data stored on Microsoft 365, then set up a new account through Account Hub and select the Microsoft Graph option.
Not all users need to act. Those using IMAP with on-premises Exchange or Microsoft 365 hosted accounts, or EWS with on-premises Exchange, require no changes. On-premises Exchange servers do not implement the Graph API, so Thunderbird's EWS support remains the primary connection method for those users.
The current Graph support covers email only, matching the scope of Thunderbird's EWS implementation; Calendar and Address Book functionality are not yet supported with either protocol. The Thunderbird team says it has begun work on Microsoft 365-hosted calendar support via Graph, describing it as the first new calendar protocol added to Thunderbird in many years.
The Graph implementation was built faster than the earlier EWS work, taking four months to enable basic synchronization compared with 11 months for EWS, which the team credits to the architecture developed for EWS support. The team says it is optimistic the same architecture will extend to future protocols such as JMAP.
Thunderbird's ESR users on Microsoft 365 will need to move to the Release channel to access the Graph API support. The announcement follows the release of Thunderbird 153 "Meadow" in July, which introduced a redesigned Account Hub for first-time setup.
