---
title: "Grade a domain's email-authentication and DNS-security..."
method: GET
path: "/api/domain/email-security"
tags: ["domain"]
---

# Grade a domain's email-authentication and DNS-security...

`GET /api/domain/email-security`

## Request

- Base URL: `https://2s.io`
- URL: `https://2s.io/api/domain/email-security`
- Auth: API key in header `PAYMENT-SIGNATURE`

Grade a domain's email-authentication and DNS-security posture from live DNS in one call: SPF, DMARC (policy + alignment), DKIM (for the supplied or common selectors), MTA-STS, TLS-RPT, DNSSEC, CAA, and BIMI. Pass domain (and optional dkimSelector). Returns an overall letter grade, a summary (spf/dmarcPolicy/dkim/mtaSts/dnssec/caa/bimi + spoofingProtected), and a per-mechanism block with the raw record, parsed tags, and specific issues (e.g. 'DMARC p=none — monitor only', 'SPF ~all soft-fail', 'no MTA-STS'). Sourced from live public DNS via DNS-over-HTTPS — an LLM cannot know a domain's current records. For deliverability/anti-spoofing audits, vendor security review, and phishing-resistance checks. DKIM is selector-based (selectors aren't enumerable), so 'not found' only means none of the checked selectors resolved.

## Query parameters

- `domain` string, required
- `dkimSelector` string
- `trial` 1

## Other responses

- `200` (unresolved $ref)
- `400`: Invalid request — not charged. error.code: BAD_REQUEST or INVALID_PARAM (parameter validation; error.details.issues lists each problem), MALFORMED_JSON, or a request-specific code. Other client errors: 405 METHOD_NOT_ALLOWED (wrong verb; see the Allow header), 413 PAYLOAD_TOO_LARGE.
- `402`: Payment required. Body is the x402 PaymentRequirements envelope with a multi-network accepts array; the per-call price is in accepts[].amount (and on the operation as x-2s-price). Sign for whichever rail you hold USDC on (EIP-3009 for Base, partial SPL transfer for Solana) and retry with the PAYMENT-SIGNATURE header (X-PAYMENT also accepted for v1 clients). Also PAYMENT_SETTLE_FAILED (error envelope) when a verified payment failed to settle: error.details.chargeStatus is "not_charged" (retry with a fresh payment) or "unknown" (the authorization may still settle before its deadline — check it before retrying).
- `429`: Too many requests — RATE_LIMITED: our per-IP / per-payer limiter. Not charged; retry after Retry-After.
- `5XX`: Server-side failure. 500 INTERNAL: unexpected error; quote error.errorId (also the X-2s-Error-Id header). 502 UPSTREAM_UNAVAILABLE (or another UPSTREAM_* code): the data provider failed — composite endpoints refuse unbilled when every source fails. 503 SERVICE_PAUSED: endpoint paused by the operator kill switch, retry after Retry-After; 503 SPEND_CAP: daily upstream budget exhausted. 504 UPSTREAM_TIMEOUT. Not charged.

---

[API](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api.md) · [All operations](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/llms.txt) · [OpenAPI document](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/revisions/da4c5caf686e?raw)