Guides · API

Email verification API

Email verification and validation for signup, CRM, lead and outreach agents: RFC syntax, live DNS mail routing (MX, null MX, implicit MX), 9,000+ disposable/throwaway domains, role addresses (info@, sales@), free providers, typo suggestions (gmial.com to gmail.com) and the domain SPF/DMARC setup. One verdict: deliverable, risky or undeliverable. Domain lookups cached for speed.

0.002 USDC per call · GET /v1/email/verify · free preview at /v1/email/verify/preview

Parameters

Name	Required	Description
`email`	yes	Email address to verify, e.g. jan.jansen@example.nl

Example request

curl "https://factline.dev/v1/email/verify?email=jan.jansen%40gmial.com"
# 402 Payment Required: pay with an x402 client (USDC on Base), or send
# Authorization: Bearer <your Factline API key>

Example response

{
  "email": "jan.jansen@gmial.com",
  "verdict": "risky",
  "reasons": [
    "disposable (throwaway) email domain",
    "possible typo of gmail.com"
  ],
  "syntax_valid": true,
  "domain": "gmial.com",
  "mail_routing": {
    "domain_exists": true,
    "accepts_mail": true,
    "mx": [],
    "implicit_mx": true,
    "null_mx": false
  },
  "disposable": true,
  "role_account": false,
  "free_provider": false,
  "suggestion": "jan.jansen@gmail.com",
  "domain_security": {
    "spf": false,
    "dmarc_policy": null
  },
  "explain": {
    "verdict": "deliverable: domain receives mail and nothing suspicious; deliverable_role: same but a shared inbox; risky: disposable domain or likely typo; undeliverable: bad syntax or the domain cannot receive mail.",
    "limits": "No SMTP mailbox probe: this confirms the domain can receive mail, not that this exact mailbox exists.",
    "disposable_list": "disposable-email-domains blocklist (CC0), 2026-10-07"
  },
  "source": "DNS via Cloudflare 1.1.1.1 (DNS-over-HTTPS); disposable-email-domains (CC0)"
}

Use it from an AI agent

Agents with an x402 wallet call the URL directly and pay per request. Assistants that speak MCP connect to https://factline.dev/mcp. Full reference: docs, OpenAPI, llms.txt. Businesses: API keys with a free trial.

Questions

How much does the Email verification cost?

0.002 USDC per call, paid per request with x402 (no account), or included in a Factline API key plan with a free trial. Calls that fail are not charged.

Can I try it for free?

Yes: GET /v1/email/verify/preview with the same parameters validates your input and shows what the paid answer contains, at no cost.

Where does the data come from?

Official public registers and open data, named with their licence in every response (source field) and at /.well-known/x402-license-provenance.