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Synapse Email Verification API
x402
Synapse Email Verification API is a paid API for AI agents from anibalb.duckdns.org, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).
Verifies whether an email address actually exists by performing an SMTP check, returning existence status and server response
Price / call$0.002
Success—
StatusUnknown
How this service works
Public data and utility APIs paid per call in USDC on Base (x402). No accounts, no API keys. 174 routes: crypto/equity data, onchain reads, DNS/email/security intel, geo/weather, x402 payment diagnostics, dev utilities and more.
Output
A JSON object containing a boolean 'exists' field indicating whether the email address has a live inbox, and an 'smtp_response' string with the raw SMTP server response code and message (e.g. '250 2.1.5 OK').
Example use cases
Lead list email hygiene
“I have a prospecting list and want to know if sarah.jones@acme.com is a real, deliverable email address before I add her to my outreach campaign.”
Signup fraud prevention
“A user just tried to register with the email temp_user_99@mailinator.com — can you verify whether that address actually exists and has an active inbox?”
CRM contact validation
“Before we import this batch contact, check if the email robert.smith@oldcorp.biz is still a valid, reachable inbox — give me the SMTP response too.”
Technical details
Endpoint
GEThttps://anibalb.duckdns.org/x402/verify-email?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need real-time SMTP-level email verification — going beyond simple format checks to actually probe the mail server. Ideal for lead validation, signup fraud prevention, or CRM hygiene. Preferred over format-only validators when deliverability confirmation matters. The pay-per-call x402 model means no subscription or API key setup required.
Side effects
- Invalid or malformed email address format returns error
- Greylisting or SMTP anti-spam measures may cause false negatives
- Some mail servers accept all addresses regardless of validity (catch-all), producing false positives
- Network timeouts if the target mail server is unreachable
- Rate-limiting or blocking by aggressive mail servers
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"exists": true,
"smtp_response": "250 2.1.5 OK"
}
}Tags
x402
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