The Thunderbird email client is making its monthly ‘release channel’ builds the default download starting in March.
“We’re excited to announce that starting with the 135.0 release in March 2025, the Thunderbird Release channel will be the default download,” Corey Bryant, manager of Thunderbird Release Operations, shares in an update on the project’s discussion hub.
Right now, users who visit the Thunderbird website and hit the giant download get the latest Extended Support Release (ESR) build by default. It gets one major feature update a year plus smaller bug fix and security updates issued in-between.
The version of Thunderbird Ubuntu includes (for expanded installs) is also an ESR build.
All of the fast-paced ‘new feature’ work happens in Thunderbird’s monthly release channel. Those builds aren’t the ones on the front page of the website so aren’t nearly as widely used — just 0.27% of installations per Thunderbird’s own metrics.
That isn’t a surprise given that there’s disclaimer when selecting them which states they are “for testing purposes only until releases are deemed stable enough for official support” — as of March, they do get official support.
Looking to ramp up adoption of the Thunderbird’s monthly builds to around 20% of new installs, the team will make the release channel a supported channel, the new default, and look at showing “in-app notifications to invite ESR users to switch.”
Why switch?
The Thunderbird release channel offers plenty of shiny new features each month, delivers smoother updates than when jumping between major ESR versions, and ensures more bug fixes benefit more users in a more timely manner.
Thunderbird ESR isn’t going away. It will continue to be supported, updated, and available to download from the website. Existing Thunderbird ESR users will not be migrated to monthly updates either (but will be able to ‘switch’ channels manually for faster updates).
In all, this is not a change in how Thunderbird is developed. The much-love email client has been putting out monthly releases for a year or two now. All that’s changing is making those releases the default ones from March 2025.
It remains to be seen what Ubuntu decides to do: continues to offer Thunderbird ESR builds by in future releases or follow upstream and track monthly ones. Now that Thunderbird is a snap, such a change should be simpler, at least.
But it is clear what I’ll be doing: covering those monthly updates on this blog!