Thunderbird 154 was released on August 18 as the latest monthly build of Mozilla’s email client, and it finally addresses a complaint that has followed the application for most of its existence.

System tray mode

Closing Thunderbird’s last window no longer has to terminate the application. With the optional system tray mode enabled, the client keeps running in the background and stays reachable from the tray.

This matters because of how mail notifications work. Thunderbird can only tell you about new mail if it is running, and for years the only way to keep it running was to leave a window open. Users who wanted background mail checking without a window on screen had to reach for extensions, and extensions that hook window management have historically been the first thing to break on a major version bump.

Having it built in removes that fragility. It is opt-in, so nothing changes unless you turn it on.

Microsoft Graph

Thunderbird 154 enables Microsoft Graph for Microsoft 365 accounts. Graph is Microsoft’s API platform for accessing Microsoft 365 services, and using it rather than legacy protocols matters as Microsoft continues tightening what it permits over basic authentication and older interfaces.

The support is currently limited to email. Calendar is not supported yet, which is worth knowing before you migrate a work account expecting full parity.

Attachments and search

The release improves attachment handling in a few concrete ways. There is a new “Copy To” folder context menu for message/rfc822 attachments, and you can now drag those attachments directly into the folder tree. If you deal with forwarded messages as attachments regularly, this removes a save-then-import round trip.

Global search picks up the option to open results in list view by default, which is a small thing that will please anyone who found the default results view unhelpful.

macOS users get attachment previews, though that is less relevant here.

Getting it

# Flatpak
flatpak update org.mozilla.Thunderbird

# Debian and Ubuntu
sudo apt update && sudo apt install --only-upgrade thunderbird

# Fedora
sudo dnf upgrade thunderbird

# Arch
sudo pacman -Syu thunderbird

Distribution packaging lags upstream by varying amounts. The Flatpak and Mozilla’s own tarball are the fastest routes if you want it immediately.

Release cadence note

Thunderbird moved to monthly releases some time ago, and the project has signalled that the pace is increasing further from September. That means version numbers will keep climbing quickly, and a jump from 153 to 154 represents a month of work rather than anything dramatic.