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Thunderbird

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Free & open-source email software and productivity solutions for managing your personal and professional communications.

San Francisco, CA

Software Development
51–200 people

About

Thunderbird is the leading free and open-source email, calendaring, newsfeed, and chat client with more than 20 million active monthly users across Windows, macOS, and Linux. One of Thunderbird's core principles is the use and promotion of open and decentralized standards. Thunderbird is part of MZLA Technologies Corporation, a wholly-owned subsidiary of the Mozilla Foundation.

Open positions

Senior Software Engineer, Cloud Engineering

Remote · Canada, United States

Build, maintain, and improve Mozilla’s internal developer infrastructure platform, including CI/CD, observability, Kubernetes optimization, environment bootstrapping, and cost optimization. Guide technical decisions, develop agentic workflows and platform features, support cross-functional delivery, and help teams operate services safely and effectively.

Senior Software Engineer, Cloud Engineering

Remote · Canada

Build, maintain, and mature Mozilla’s internal developer infrastructure platform, including CI/CD, observability, Kubernetes optimization, environment bootstrapping, and cost optimization. Guide technical decisions, improve developer productivity through agentic workflows, mentor teammates, collaborate across functions, and develop platform proposals and features.

Software Engineer, Firefox Desktop Integrations

Remote · Canada

Help develop and maintain Firefox installation, update, and operating-system integration features, with a focus on Windows and macOS. Collaborate with teammates on scoped engineering tasks, participate in code reviews, and identify and fix bugs that improve the browser experience.

Sr. Staff Software Engineer, Browser (New Products)

Remote · Canada, United States

Design and implement browser-engine experiments and prototypes, investigating how browser internals affect performance, correctness, and programmatic interaction with web content. Instrument and evaluate changes using repeatable tasks, profiling, and testing, then document results and tradeoffs to inform technical direction.