# how.is Email Authentication Checker

> how.is Email Authentication Checker is a paid API for AI agents from how.is, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-31).

Retrieves and evaluates SPF, DKIM, and DMARC DNS records for a domain, returning an overall email authentication posture score and recommendations.

## Facts

- Endpoint: POST https://how.is/v1/domain/email-auth?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/how-is-email-authentication-checker-33c8231f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_5ngDHVWlviLbZAjoFqsHC

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 how-is-email-authentication-checker-33c8231f -d '<json body>'
```

Example prompt: Can you check the email authentication setup for stripe.com — I want to see their SPF, DKIM, and DMARC records and whether the overall posture is solid?

## When to prefer this

Use this endpoint when you specifically need to inspect and score a domain's email authentication posture (SPF, DKIM, DMARC) in one call, rather than manually querying individual DNS records. It is the right choice when auditing email deliverability, assessing phishing exposure, or verifying a domain's anti-spoofing configuration, and it pairs well with other how.is sibling endpoints (e.g. blocklist checks, domain age) for a complete domain security profile.

## Known failure modes

- Invalid or malformed domain name returns a validation error
- Domain not found in DNS returns empty or null records for SPF/DKIM/DMARC
- Domain with no email authentication records returns low score with recommendations
- Network timeout during DNS lookup may return an error or partial data
- Domains exceeding 253 characters are rejected by schema validation

## How this service works

SPF, DKIM and DMARC records and posture for a domain.

## Output

Returns a JSON object containing parsed SPF, DKIM, DMARC, and MX records, an overall numerical score, an overall status label, and a list of actionable recommendations for improving email authentication posture, along with a payment receipt confirming the x402 micro-payment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "domain": {
   "type": "string",
   "maxLength": 253,
   "description": "A bare domain name, e.g. example.com"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": {
   "_shape": "data.data: spf, dkim, dmarc, mx, overallScore, overallStatus, recommendations."
  },
  "result": "Email authentication for the requested subject",
  "receipt": {
   "rail": "x402",
   "tool": "email-auth",
   "charge_usd": 0.005,
   "settlement_tx": "0x…"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/how-is-email-authentication-checker-33c8231f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from how.is](https://www.zero.xyz/host/how.is/llms.txt)