Best pay-per-call APIs to verify business email address deliverability without sending email for AI agents (October 2026)

Verifies whether a given email address is valid and deliverable using Hunter's email verification service, billed per-call via x402 micropayments.

Submits a list of email addresses or CSV text for asynchronous bulk validation, returning syntax, domain, MX, disposability, typo, and real-bounce verdicts with quality scores.

Verifies an email address for deliverability, checking MX records, SMTP validity, disposable status, and spam risk score

Checks if a single email address is likely to bounce using a waterfall of validation strategies, including catch-all detection

Validates email deliverability via syntax check, MX record lookup, and SMTP reachability, returning a risk score and quality rating.

Verifies whether a given email address is deliverable using live SMTP checks, returning deliverability status, provider, and spam/catch-all signals

Verifies whether an email address is deliverable by performing SMTP mailbox probing (RCPT TO) and MX record checks without sending any email.

Validates an email address by checking format, domain MX records, disposability, and role-address status

Validates an email address for deliverability, detects disposable/temporary domains, identifies role-based addresses, verifies MX records, and returns a trust score and letter grade.

Validates an email address across syntax, domain, MX records, disposable/role/freemail checks, typo suggestions, and optionally performs an SMTP handshake to verify mailbox existence.