Thunderbird, the open-source email client, has crossed a significant funding milestone: in 2024 it raised USD 10.3 million in donations, the first time its annual intake has surpassed the $10 million mark.
In 2024, the Thunderbird project recorded 335,000 individual donors, contributing via over 539,000 transactions. This marks a 19% increase in total donation revenue compared to 2023. Despite that growth, donation levels remained modest: the average contribution was around USD 18.88, with a median gift of USD 16.66. Among recurring donors, the average monthly donation was USD 6.25.
Most donations were small: 53% were USD 20 or less, and 94% were USD 35 or less. Only 17 donations in 2024 reached USD 1,000 or more—underscoring that Thunderbird’s funding comes largely from many modest contributors rather than a few large benefactors.
Geographical breakdown of contributions
Thunderbird’s donor base is global, with contributions from over 200 countries. The top ten contributing countries accounted for 83 % of total revenue.
Germany led the contributions, supplying about one third of the total. The United States followed with 18% of revenue, and France contributed around 7%. Dutch donors accounted for roughly 4 %, amounting to €412,000 in 2024.
Users, team size, and expenditures
Thunderbird serves more than 20 million users. The project currently employs 43 full-time staff, up by 14 over the course of 2024 as various new roles were added in development, mobile, infrastructure, and community support.
A large share of the budget goes to staff costs. Other significant expenses include infrastructure, operational support, and administrative overhead.
Product developments and roadmap
In 2024 Thunderbird expanded beyond its desktop roots. The team launched Thunderbird for Android in October, following the integration of the K-9 Mail codebase and a full redesign of interface and functionality. Work is underway on a Thunderbird version for iOS, being built from scratch using modern foundations (JMAP) to enable efficient synchronization and performance.
On the desktop side, Thunderbird introduced a monthly release channel to supplement its long-term support (ESR) updates. The aim is to deliver features and improvements at a faster cadence while preserving stability.
Beyond the client, the Thunderbird team is developing new services under “Thunderbird Pro,” including Thundermail (a privacy-oriented webmail alternative), Appointment (a scheduling tool), and Send (encrypted file sharing).
Significance and transparency
The 2024 fundraising milestone is notable not just for its scale, but for its democratic character: Thunderbird’s developers emphasize that the project is sustained by a broad global community rather than a small number of large donors.
The published “State of the Bird 2024/25” report lays out donation, expense, and product development details, underlining the project’s commitment to transparency.
