The Thunderbird team says it's very close to achieving Microsoft Exchange support

The Thunderbird team has released its May dev digest, revealing significant advancements for the popular open-source email client. The upcoming beta version 128 will feature Rust-enabled builds by default, allowing users to test experimental features. Progress on Microsoft Exchange support is promising, with the main flow completed, enabling account setup, folder fetching, and message display, though some final touches remain.

Additionally, Thunderbird now supports Linux system tray and DBus hooks, enhancing its integration with the OS. The much-anticipated folder pane multi-selection feature is nearing completion and should be available soon. Version 128 will also introduce account color customization, providing visual cues in the message list and compose window for users with multiple accounts. Lastly, Thunderbird now supports native Windows 10/11 notifications, improving the user experience on these platforms.