BounceZero runs every email through a 5-stage pipeline: syntax, MX/DNS, real-time SMTP probing, provider-specific checks (Gmail, Outlook, Yahoo, ProtonMail + 20 more), and an AI scoring engine that returns a confidence score from 0–100. Results: verified / likely_valid / risky / catch-all / invalid — in under 2 seconds. What's different: • AI scoring catches what rule-based tools miss • 100 free credits every month, no card required • Credits never expire — no subscription pressure