# Email Validation API (Syntax + MX DNS Check)

> Email Validation API (Syntax + MX DNS Check) is a paid API for AI agents from gateway.stride20k.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-10).

Validates an email address via RFC-style syntax checking and live MX-record DNS lookup, returning a deliverability flag, parsed domain, and sorted MX hosts — without storing data or verifying mailbox existence.

## Facts

- Endpoint: GET https://gateway.stride20k.com/email/validate/:email?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/email-validation-api-syntax-mx-dns-check-d759f3ae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xulIg2Wjl1DDBSoXk1BMQ

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-validation-api-syntax-mx-dns-check-d759f3ae
```

Example prompt: Can you check whether john.doe@example.com is a valid, deliverable email address — specifically confirm the syntax is correct and that the domain actually has MX records set up to receive mail?

## When to prefer this

Use this endpoint when you need a fast, privacy-respecting email validation that combines RFC syntax checking with real DNS MX-record lookup in a single call, without relying on third-party enrichment services or storing data. Prefer it over pure regex validators when DNS deliverability matters, and over SMTP-level verifiers when you don't need (or want) actual mailbox probing. Ideal for lead cleaning, signup form validation, and pre-send contact verification in agent workflows.

## Known failure modes

- Malformed email path param returns syntaxValid:false with deliverable:false and null domain
- Domain with no MX and no A record returns deliverable:false and aFallback:false
- DNS resolution timeout or DoH upstream failure may return an error response
- Cached responses up to 1 hour old may not reflect recent DNS changes
- Mailbox existence is never verified — deliverable:true does not mean the inbox exists

## How this service works

Email validation API: RFC-style syntax check plus live MX-record lookup (with RFC 5321 A-record fallback) over DNS-over-HTTPS — no third-party service, nothing stored. Returns parsed domain, sorted MX hosts, and a 'deliverable' flag meaning DNS will accept mail for the domain — it does NOT verify the mailbox exists. Use for lead cleaning, signup validation, and contact verification by agents. Cached up to 1 hour per address.

## Output

Returns a JSON object with: a boolean syntaxValid (RFC syntax check), a boolean deliverable (true if domain has MX records or an A-record fallback per RFC 5321), the parsed lowercase domain, an array of MX host records sorted by preference, hasMx and aFallback booleans, plus metadata including whether the response was served from cache (up to 1-hour TTL) and the ISO 8601 timestamp of the upstream DNS fetch.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/email-validation-api-syntax-mx-dns-check-d759f3ae/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gateway.stride20k.com](https://www.zero.xyz/host/gateway.stride20k.com/llms.txt)