SMTP-verify the business emails on saved leads through MillionVerifier. Included in every plan at no charge; a re-check within 90 days reuses the cached verdict. Runs in the background and returns a job id: poll get_job_status with kind "verify" until status is completed, then read the summary. Each address ends in one of four honest states: verified, catch_all (the domain accepts everything, so deliverability cannot be proven), unknown, or invalid. Never treat catch_all as verified.