In this latest State of the Thunder, we're discussing the upcoming yearly ESR, 140.0, which is due out June 24, 2025. We explain our numbering convention and our different channels, which comes from Firefox, and the difference between ESR, Release, Beta, and Daily. Find out why we're encouraging to use the monthly Release channel, but how this won't take anything away from ESR. Learn more about what channel is right for you (especially if you use add-ons), how to help us with using Beta and Daily, and how to safely move between ESR and Release. And as always, we finish with a community shoutout!

Resources:

• What Train is It Now: http://whattrainisitnow.com
• Monthly Release Channel Blog Post: https://blog.thunderbird.net/2025/03/thunderbird-release-channel-update/
• Choosing a Release Channel: https://support.mozilla.org/kb/choosing-thunderbird-release-channel
• Testing Beta Support Article: https://support.mozilla.org/kb/thunderbird-beta
• Testing Daily Support Article: https://support.mozilla.org/kb/thunderbird-daily
• Release Channel Support Article (with info on safely downgrading): https://support.mozilla.org/kb/thunderbird-release
• Add-on Compatibility Add-on: https://addons.thunderbird.net/thunderbird/addon/addon-compatibility-check/
• tilorenz's Calendar grid patch: https://phabricator.services.mozilla.com/D251992