Founding Backend Engineer

Founding Engineer: Build the Email Infrastructure for AI Agents What happens when millions of AI agents need their own email addresses? We're not talking about adding AI to Gmail — we're talking about rebuilding email infrastructure specifically for a world where AI agents communicate, authenticate and operate autonomously. A fast-growing, $6M-funded startup in San Francisco is building exactly that: an API-first email platform that lets developers create and manage inboxes for AI agents at scale. They're looking for a backend-leaning Founding Engineer to join the early team and help build the core infrastructure from the ground up. What You'll Do: 🤖 Build Infrastructure for AI Agents – Design the APIs and backend systems agents use to communicate, authenticate and interact with the real world. ⚡ Own 0→1 Projects – Take major projects from idea through system design to production, from IMAP integrations to usage-based pricing infrastructure. 🏗 Solve Hard Backend Problems – Work across distributed systems, databases, developer tooling and email protocols while processing hundreds of thousands of emails every day. 🚀 Shape the Product – Work directly with customers, propose new products and growth experiments, and help determine what the company builds next. What They're Looking For: ✔ 0–5 years of software engineering experience, with flexibility for exceptional candidates outside this range. ✔ Strong backend engineering skills and experience shipping production software at a leading tech company or high-growth startup. ✔ Evidence you've built things from 0→1 and can independently own projects end-to-end. ✔ Comfortable working across the stack when required, although the role is approximately 80% backend. ✔ Excited by early-stage startups, high ownership and building directly alongside a founding team. Why Join? 💰 $160,000–$250,000 base 📈 0.5–1% founding-team equity 🏢 Five days per week in San Francisco, building alongside a small, ambitious team. 🚀 $6M raised to build a new category of infrastructure for the rapidly growing AI agent ecosystem. This isn't about putting an AI assistant inside an existing email product. It's about building the underlying email infrastructure that AI agents themselves will use — and joining early enough to shape how that infrastructure gets built.