Senior Mobile Engineer, iOS - Mozilla

Why Thunderbird?

Thunderbird is one of the world’s most trusted open-source email applications, empowering more than 20 million people globally. At MZLA, the team behind Thunderbird, we build privacy-respecting communication and productivity tools that help people manage their digital lives while staying in control of their data.

We are open source by design. Our products are developed transparently and in collaboration with a global community of contributors, and that same spirit shapes how we work: collaboratively, inclusively, and with a shared commitment to putting users first.

The Opportunity

The Senior Software Engineer, iOS is an experienced individual contributor who brings deep iOS expertise to the design, development, and evolution of Thunderbird’s iOS application. You’ll work closely with mobile engineers, product management, UX, and other partners to deliver a high-quality iOS experience that meets high standards for performance, reliability, accessibility, security, and maintainability.

What You’ll Do

• Build and refine Thunderbird’s mobile products and platform architecture.
• Improve scalability, performance, reliability, and user experience.
• Develop a deep understanding of the codebase and architecture to confidently make changes across the entire stack.
• Maintain strong debugging and testing practices across unit, integration, and automated testing.
• Review code and guide improvements to architecture, testing, and development best practices.
• Independently resolve complex issues involving performance, security, and cross-platform integration.
• Monitor application health and address issues before they escalate.
• Document technical decisions, system architecture, and team processes.
• Own assigned projects, collaborating cross-functionally, from investigation and planning through development, validation, and delivery.
• Ensure mobile development meets accessibility, security, and privacy standards.

What You Bring

• 7+ years of professional software development experience, including 2+ years in a Senior Software Engineer role.
• 3+ years of professional mobile application development experience.
• Strong experience with Swift, SwiftUI, and iOS frameworks.
• Deep knowledge of iOS architecture, design patterns, and performance optimization.
• Experience delivering and maintaining complex, scalable, and reliable software.
• Experience addressing technical debt and refactoring large or complex codebases.
• Strong knowledge of mobile security, including encryption, secure storage, app signing, and vulnerability remediation.
• Experience with communication and email protocols such as RSS, IMAP, POP, or Matrix, and familiarity with IETF standards for CalDav or CardDav.
• Advanced proficiency with Git and collaborative development workflows.
• Strong debugging, testing, and problem-solving skills.
• Strong attention to detail, curiosity, and a product-focused mindset.
• The ability to work independently, take ownership, and collaborate across teams.
• Excellent async written communication skills; comfortable working with a geographically distributed team.
• Ability to learn, evaluate, and responsibly use emerging technologies, including AI-enabled tools, to improve work processes.

Compensation & Benefits

• Base Salary Range (Canada): $108,000 - $125,000 CAD
• Fully remote work & schedule flexibility
• Company-provided laptop
• Annual bonus program & professional development stipend
• 24 days PTO per year, wellbeing days, public holidays, and year-end shutdown
• Comprehensive health, dental, vision, life, and disability insurance
• RRSP contributions and employee assistance program
• Paid parental leave