Staff Engineer, Front End; Desktop

MZLA Technologies Corporation (MZLA) is a wholly owned, for-profit subsidiary of the Mozilla Foundation and home to Thunderbird , our flagship open-source email and productivity platform empowering more than 20 million people around the world. While part of the Mozilla portfolio of companies, MZLA operates independently in both identity and organizational structure from the Mozilla Foundation and Mozilla Corporation.

Everything we build at MZLA is open source, developed transparently and in collaboration with a global community of contributors. This open approach shapes not only our products but also how we work: collaboratively, inclusively, and with a shared commitment to building technology that puts users first. We believe privacy and productivity should coexist , and that people deserve powerful digital tools without surrendering control of their data.

MZLA is a small but growing team of 50+ people distributed across seven countries . As we evolve Thunderbird from a single application into a suite of privacy-respecting productivity tools, we’re introducing new products and services that remain independent of big tech ecosystems . Our unique revenue model combines community donations that keep Thunderbird freely available with subscriptions for new cloud-based services, allowing us to grow and innovate while remaining independent and true to our values.

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As a Staff Software Engineer, Front-End , you’ll serve as a domain expert who deeply understands the complexities of shaping seamless, user-focused interfaces and delivering high-quality front-end solutions that align with product strategy. You’ll join a team of talented front- and back-end engineers who bring deep expertise to the development and maintenance of our flagship desktop application, cherished by millions of users worldwide for over 20 years.

You’ll work closely with engineers and cross-functional partners to tackle ambiguous problems in user experience, performance optimization, and architectural design. The ideal candidate has a strong focus on front-end architecture, user experience, and performance, and demonstrates technical leadership, sound judgment, and a collaborative approach to problem solving.

You’ll play a vital part in translating strategy into action by influencing technical direction, mentoring engineers at multiple levels, and ensuring that technical decisions align with MZLA’s mission and the objectives of the Thunderbird Project, particularly in delivering exceptional user experiences.

This is a full-time, remote position working with colleagues across multiple regions and time zones.

• Lead complex, ambiguous technical initiatives requiring cross-team and cross-organization coordination
• Own and deliver projects spanning new features, code quality improvements, tooling, and process optimization
• Partner with senior engineers and product managers to define and execute technical strategy, reduce technical debt, and improve long-term maintainability
• Collaborate closely with UX Engineers to ensure accessibility and usability are built in from the start (WCAG, ARIA)
• Establish and promote scalable front-end architecture through shared frameworks and guidelines
• Write high-quality, testable, and maintainable code; contribute to code reviews, testing, regression triage, and patch integration
• Mentor and support engineers across the team, fostering a culture of learning and continuous improvement

• 10+ years of experience in front-end software development, building scalable, maintainable, and user-focused systems.
• Extensive knowledge of modern vanilla JavaScript concepts (module patterns, async and promises, custom elements and shadow DOM), and up to date knowledge with the most recent ECMAScript specification.
• Strong command of modern JavaScript frameworks such as React, Vue, or similar, and experience transitioning legacy codebases to new technologies.
• Deep knowledge of HTML5 structures and advanced accessibility patterns and Deep knowledge of modern CSS patterns and methods.
• In-depth understanding of system architecture, design patterns, and software engineering best…