Mobile Engineer, iOS

Why Thunderbird?

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.

To learn more, visit

The Staff Software Engineer, Mobile is a senior individual contributor who brings deep iOS expertise to the design, development, and evolution of Thunderbird’s iOS application. This role works on complex and ambiguous technical problems, leads significant mobile initiatives, and contributes to architectural decisions in collaboration with other senior engineers and engineering leadership.

You’ll work closely with mobile engineers, product management, UX, and other partners to deliver high‑quality iOS experiences that meet high standards for performance, reliability, accessibility, security, and maintainability. The ideal candidate demonstrates deep mobile expertise, collaboration with engineering leadership and peers, ownership of technical decisions, and the ability to influence, mentor, and guide the work of other engineers.

You’ll play a critical role in delivering exceptional user experiences by translating strategy into action and ensuring technical decisions align with MZLA’s mission and the objectives of the Thunderbird Project. This is a full‑time, remote position working with colleagues across multiple regions and time zones.

• Tackle complex and ambiguous technical challenges in mobile development that require thoughtful design, planning, and coordination.
• Serve as a technical lead on major iOS initiatives, including feature development, architectural improvements, and targeted refactoring.
• Collaborate with senior engineers and engineering leadership on mobile technical direction and architectural decisions.
• Drive improvements to code quality by reducing technical debt and improving performance, stability, and build health.
• Partner closely with product and UX teams to ensure usability and accessibility are integral to iOS implementations.
• Write high‑quality, testable, and maintainable iOS code, contributing to a consistent and reliable codebase.
• Mentor and support other engineers through code reviews, technical guidance, and knowledge sharing.
• Contribute to improving engineering practices and workflows, and stay current with iOS technologies and best practices.

• 10+ years of professional software development experience, including significant experience working on complex mobile applications at senior level.
• Deep experience with Swift and iOS frameworks required.
• Expertise with mobile architectures, platform constraints, and application lifecycle management on iOS.
• Proven experience leading complex technical work and contributing to architectural decisions, with the ability to act as a technical lead and mentor supporting the growth of other engineers.
• Solid understanding of software engineering best practices, including system design, testing strategies, and release…