Why this pre-filter keeps unknown instead of guessing

If you are deciding what to send to a paid verifier, a useful first pass is to separate four things: syntax/typo, public DNS/MX, disposable signals, and role addresses. Ambiguous rows stay unknown; this is not SMTP probing, mailbox login, sending, or a deliverability guarantee. It is for buyer-owned lists and is bounded to 500 rows per run. I built the starter kit and maker notes here: https://whop.com/checkout/plan_QkeyoS478L2hH/