Ksenda is a multi-tenant cold-email SaaS with per-user BYOK (Apollo for leads, Gemini for AI-presence targeting, Gmail SMTP for delivery). The motivation: most cold-email tooling either pools your sender reputation with strangers or ships as a CRM bolt-on that ignores deliverability. Ksenda lets every user keep their own keys and own their sender reputation while still getting AI targeting and automation. Solo-built with: - Next.js 16 + React 19 frontend; Prisma 7 + libSQL backend with 14 data models for multi-tenant isolation - Threaded follow-ups on Day 3/7/14 via Gmail In-Reply-To / References headers (keeps replies in-thread, not as new emails that destroy continuity) - Gemini AI-presence targeting to filter prospects before sending - 5-state automation pipeline with five independent campaign toggles Validated on BrandVox's own outbound: ~15% reply rate on 5,000+ emails (vs ~3-5% industry average, Instantly 2026 benchmark). Website: https://ksenda.com GitHub: https://github.com/egehakan/ksenda