Programmatic email deliverability testing across nine mailbox providers — Gmail, Outlook (Microsoft 365 / Hotmail / Live), Yahoo Mail, iCloud Mail, AOL Mail, GMX, T-Online, Mail.ru and Yandex. Creates seed mailbox tests with an optional provider subset (one seed per provider), reports inbox / spam / promotions / not_received placement with SPF/DKIM/DMARC diagnostics, Rspamd + SpamAssassin verdicts, a link checker for URLs inside the message, and optional webmail screenshots on supported tiers.