• Development

Thunderbird Monthly Development Digest – March 2025

Hello again Thunderbird Community! It’s been almost a year since I joined the project and I’ve recently been enjoying the most rewarding and exciting work days in recent memory. The team who works on making Thunderbird better each day is so passionate about their work and truly dedicated to solving problems for users and supporting the broader developer community. If you are reading this and wondering how you might be able to get started and help out, please get in touch and we would love to get you off the ground!

Paddling Upstream

As many of you know, Thunderbird relies heavily on the Firefox platform and other lower-level code that we build upon. We benefit immensely from the constant flow of improvements, fixes, and modernizations, many of which happen behind the scenes without requiring our input. 

The flip side is that changes upstream can sometimes catch us off guard – and from time to time we find ourselves firefighting after changes have been made. This past month has been especially busy as we’ve scrambled to adapt to unexpected shifts, with our team hunting down places to adjust Content Security Policy (CSP) handling and finding ways to integrate a new experimental whitespace normalizer. Very much not part of our plan, but critical nonetheless.

Calendar UI Rebuild

The implementation of the new event dialog is moving along steadily with the following pieces of the puzzle recently landing:

• Title
• Border
• Location Row
• Join Meeting button
• Time & Recurrence

The focus has now turned to loading data into the various containers so that we can enable this feature later this month and ask our QA team and Daily users to help us catch early problems.

Keep track of feature delivery via the [meta] bug 

Exchange Web Services support in Rust

We’re aiming to get a 0.2 release into the hands of Daily and QA testers by the end of April so a number of remaining tasks are in the queue – but March saw a number of features completed and pushed to Daily

• Folder copy/move
• Sync folder – update
• Complete composition support (reply/forward)
• Bug fixes!

Keep track of feature delivery here.

Account Hub

This feature was “preffed on” as the default experience for the Daily build but recent changes to our Oauth process have required some rework to this user experience, so it won’t hit beta until the end of the month. It’s beautiful and well worth considering a switch to Daily if you are currently running beta.

Global Message Database

The New Zealand team completed a successful work week and have since pushed through a significant chunk of the research and refactoring necessary to integrate the new database with existing interfaces.

The patches are pouring in and are enabling data adapters, sorting, testing and message display for the Local Folders Account, with an aim to get all existing tests to pass with the new database enabled. The path to this goal is often meandering and challenging but with our most knowledgeable and experienced team members dedicated to the project, we’re seeing inspiring progress.

The team maintains their documentation in Sourcedocs which are visible here.

In-App Notifications

A few last-minute changes were made and uplifted to our ESR version early this month so if you use the ESR and are in the lucky 2% of users targeted, watch out for an introductory notification!
We’ve also wrapped up work on two significant enhancements which are now on Daily and will make their way to other releases over the course of the month:

• Granular control of notifications by type via EnterprisePolicy
• Enhanced triggering mechanism to prevent launch when Thunderbird is in the background

 Meta Bug & progress tracking.

New Features Landing Soon

A number of requested features and important fixes have reached our Daily users this month. We want to give special thanks to the contributors who made the following possible…

• Several colour scheme improvements and fixes.
• A long-standing feature request to add manual sort order for folders
• Fix to notification interaction with quick filter
• Multiple message selection correction
• and many more which are listed in release notes for beta.

As usual, if you want to see and use new features as they land, and help us squash some early bugs, you can try running daily and check the pushlog to see what has recently landed. This assistance is immensely helpful for catching problems early.

—

Toby Pilling

Senior Manager, Desktop Engineering