Staff Designer, Rapid Prototyping

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. We are a small but growing company of 60+ people distributed across seven countries. As Thunderbird evolves beyond a single desktop application, we are expanding across desktop, mobile, paid services, and new product experiences that help people and organizations work more effectively without giving up control to big tech ecosystems. Our revenue model combines user donations, which help keep Thunderbird’s apps freely available, with paid services that cover the costs of hosted offerings while supporting long-term sustainability and continued innovation. A note about MZLA and Mozilla: MZLA Technologies Corporation is the nonprofit-owned company behind Thunderbird and part of the Mozilla family. MZLA is separate from Mozilla Corporation and has its own compensation programs, benefits, and employment policies. To learn more, visit The opportunity Thunderbird is expanding beyond email with Thunderbolt, an open-source AI client designed for organizations that need more control over their data, infrastructure, and model choices. We’re looking for a Staff Designer to help shape the product experience for Thunderbolt as it moves from early product development into enterprise use cases. This role sits at the intersection of product design, front-end engineering, prototyping, and AI-assisted product development. You’ll turn early product ideas, user needs, partner feedback, and workflow concepts into working prototypes and production-ready user experiences. This is not a role focused only on mockups or design artifacts. You’ll work directly in the codebase, use AI-assisted development tools thoughtfully, and help define the interaction patterns that make Thunderbolt intuitive, useful, trustworthy, and enterprise-ready. You should be comfortable operating independently in ambiguity, moving quickly from concept to prototype, distinguishing between experiments and production-ready work, and creating reusable product and interaction patterns that help the broader team move faster. What you’ll do Build functional prototypes and product experiments directly in the Thunderbolt codebase. Translate ambiguous product ideas, user workflows, partner feedback, and enterprise needs into clear, usable product experiences. Help define interaction patterns for AI-powered chat, search, research, workflow automation, knowledge retrieval, and enterprise administr