Developers

The deliverability API

One REST call returns a full 7-check email deliverability audit for any domain: MX, SPF, DKIM, DMARC, TLS, reverse-DNS, and blocklists, scored the same way the free audit and Pro monitoring are.

No SDK to install. Bearer auth, JSON in, JSON out. 100 audits/day on Pro, 500/day on Agency.

Try it live

No account, no API key. Pick a check, enter a domain, and see the real JSON the API returns, plus the exact call to drop into your code.

Pick a check and press Run to see the live response.

Use it in your code

curl "https://inboxproof.email/api/spam-check?domain=example.com"

Try it

curl -H "Authorization: Bearer <your-api-key>" \
  "https://inboxproof.email/api/v1/audit?domain=yourdomain.com"

Your API key is on your dashboard once you're on Pro.

CLI tool

Prefer the terminal? The free inboxproof-cli runs the same 7 checks locally and prints a 0-100 score with the exact record to fix. No account, no API key.

npx github:jtc268/inboxproof-cli yourdomain.com

Open source, zero dependencies. View on GitHub.

Endpoint

GET /api/v1/audit?domain={domain}

Auth	`Authorization: Bearer <key>` (or `?key=<key>`)
domain	Required. The domain to audit, e.g. `yourdomain.com`
Rate limit	100 audits/day on Pro · 500/day on Agency

Response

{
  "ok": true,
  "domain": "yourdomain.com",
  "at": "2026-02-14T09:30:00.000Z",
  "score": 82,
  "grade": "B",
  "checks": [
    { "id": "mx",    "name": "MX & mail routing", "status": "pass" },
    { "id": "spf",   "name": "SPF",               "status": "pass" },
    { "id": "dkim",  "name": "DKIM",              "status": "warn" },
    { "id": "dmarc", "name": "DMARC",             "status": "pass" },
    { "id": "tls",   "name": "TLS",               "status": "pass" },
    { "id": "ptr",   "name": "Reverse DNS (PTR)", "status": "warn" },
    { "id": "rbl",   "name": "Blocklists",        "status": "pass" }
  ]
}

Each status is pass, warn, or fail. The score is the weighted sum (DMARC and MX carry the most), 0–100. The same engine powers the free audit and Pro daily monitoring.

Errors

401	Missing, invalid, or non-Pro API key.
400	Missing or malformed `domain`.
429	Rate limit exceeded for the day.

Free public endpoints

Four check endpoints are open with no API key, rate-limited to 20 calls/hour per IP. Good for quick lookups, scripts, and prototyping.

`GET /api/spam-check?domain={d}`	Full 7-check audit with a spam-risk verdict and the failing items to fix.
`GET /api/dmarc-check?domain={d}`	MX, SPF, DKIM, DMARC checks with a 0-100 score.
`GET /api/mx-check?domain={d}`	MX records and whether each mail server resolves.
`GET /api/blocklist-check?ip={ip}`	Checks an IP against 9 blocklists (defaults to your IP).

curl "https://inboxproof.email/api/spam-check?domain=yourdomain.com"

No auth, no account. For high volume or daily monitoring, use the Pro API above.

Transactional email API deliverability Deliverability for developers SPF, DKIM, DMARC explained How to check email deliverability SPF record checker DMARC record checker

Put it to work

Wire a daily deliverability check into your deploy pipeline, monitor client domains from your agency dashboard, or gate cold-email sends on a passing score.

Get Pro: $14.50/mo

No lock-in. Cancel anytime.