# Email Syntax and MX Domain Validator

> Email Syntax and MX Domain Validator is a paid API for AI agents from api.x-402.online, paid per call via x402, $0.005/call, status down (last checked 2026-09-15).

Validates an email address by checking its syntax and verifying the domain has valid MX DNS records, without sending any email.

## Facts

- Endpoint: POST https://api.x-402.online/v1/email/validate
- Price: $0.005/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/email-syntax-and-mx-domain-validator-c3ccd478
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6PtQikUCkKVGFvRXgRmnR

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability email-syntax-and-mx-domain-validator-c3ccd478 -d '<json body>'
```

Example prompt: Can you check if the email address john.doe@example.com is valid — both the format and whether the domain can actually receive mail — without sending anything to it?

## When to prefer this

Use this endpoint when you need lightweight, passive email validation — checking both format and deliverability signals (MX records) without triggering any email send or requiring the user to click a link. Ideal for form validation, lead qualification, or pre-send list scrubbing where speed and privacy matter.

## Known failure modes

- Malformed or missing email query parameter returns an error
- Domain exists but has no MX records — flagged as invalid for mail delivery
- Temporary DNS lookup failure may cause false negatives
- Extremely unusual but syntactically valid email formats may be misclassified

## Output

Returns a validation result indicating whether the email address passes syntax checks and whether the domain has valid MX DNS records, without dispatching any email.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/email-syntax-and-mx-domain-validator-c3ccd478/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x-402.online](https://www.zero.xyz/host/api.x-402.online/llms.txt)