E-mail verification API

What one call checks

Every address goes through the same pipeline the app uses for its own campaigns:

• Syntax and length rules (RFC 5321).
• Disposable and temporary-mail domains from a built-in list of common providers.
• Role accounts (info@, sales@, support@) that rarely answer cold mail.
• MX records: does the domain accept mail at all?
• Mailbox and accept-all check over SMTP when our server can connect to the recipient's mail server; otherwise the reason smtp_unreachable says the mailbox was not checked.

Three buckets, not a score you have to interpret

The answer is valid, risky or invalid with reason codes. Campaigns never send to addresses verified as invalid; risky ones (accept-all servers, disposable domains, inconclusive or timed-out checks) are your call. A valid result with the reason smtp_unreachable means the domain accepts mail but the mailbox itself was not checked, and catch_all is true only when the accept-all check ran.

curl -X POST https://coldleads.app/api/v1/verify \
  -H "x-api-key: sk_…" -H "Content-Type: application/json" \
  -d '{"email":"jane.doe@example.com"}'

# illustrative responses (example.com is reserved for documentation)
# mailbox not checked (no SMTP connection to the mail server)
{ "status": "valid", "score": 75, "reasons": ["smtp_unreachable"], "mx": "mx.example.com", "catch_all": false }
# mailbox confirmed over SMTP
{ "status": "valid", "score": 97, "reasons": ["ok"], "mx": "mx.example.com", "catch_all": false }

Lists and pricing

Bulk endpoint: up to 5 000 addresses per job, 5 parallel jobs, results as JSON (CSV export is in the web app). 120 requests per minute per key. 1 credit per address; the Business plan ($99/month) includes 10,000 credits and the API, extra packs cost $5 per 1 000.

Results are cached for 30 days, so re-checking the same list is fast; every check still costs 1 credit.

Billing you control from the app

Change the plan in Settings and choose when it starts — today (unused days are credited and a new billing month begins) or at the next renewal. Update the card in one click, cancel any time: a cancelled subscription keeps working until the end of the paid period. No Stripe dashboard, no e-mails to support.

FAQ