2 agent-payable APIs. Every listing carries a tested call recipe - endpoint, auth shape, pricing, and known gotchas - on its detail page. paywallwatch.com ↗
Use when an agent has an email address from a form, a scrape or a CRM and must decide whether it is worth sending to. Screens the address: syntax, DNS mail exchanger, disposable domain, role account, free provider and common typos. It does not verify that the mailbox exists. A DNS failure answers 503 and is not charged.