Free Email Deliverability API — SPF, DKIM, DMARC & Blacklist Checks

Quick start

curl -s https://aureliussdr.com/api/tools/grade \
  -H "Content-Type: application/json" \
  -d '{"domain": "example.com"}'

All endpoints accept POST with a JSON body containing domain. Responses are JSON. Rate limit: ~10–15 requests/min per IP per endpoint (HTTP 429 beyond that). For continuous monitoring of your own domains, use a free account instead of polling.

POST /api/tools/grade

The full picture in one call: SPF (with DNS-lookup counting), DMARC, DKIM discovery, MX and 10 blacklists, plus a composite grade (A–F) and score (0–100).

{"domain":"example.com"} →
{
  "domain": "example.com", "grade": "B", "score": 80, "issues": 1,
  "spf":   { "found": true, "record": "v=spf1 …", "lookups": 4, "all": "~all", "issues": [], "warnings": [] },
  "dmarc": { "found": true, "record": "v=DMARC1; p=quarantine; …", "tags": { "p": "quarantine", "rua": "…" } },
  "dkim":  [ { "selector": "google", "found": true, "keyBits": 2048 } ],
  "mx":    { "found": true, "records": ["1 aspmx.l.google.com"] },
  "blacklists": { "ips": ["93.184.216.34"], "listed": [], "checked": 17 }
}

POST /api/tools/spf

SPF record with recursive DNS-lookup counting against the RFC 7208 limit of 10 — catches the silent permerror that most checkers miss. Flags multiple records, +all, dead includes, deprecated ptr.

POST /api/tools/dmarc

DMARC record from _dmarc.<domain>, parsed tags (p, sp, rua, pct…), policy-strength issues and warnings.

POST /api/tools/dkim

Probes ~20 common DKIM selectors (google, selector1/2, k1, s1…) or a specific one via optional "selector" field. Returns key presence, revocation, and approximate key length.

POST /api/tools/blacklist

Checks the domain and its resolved IPs against 10 DNSBLs (Spamhaus ZEN & DBL, SpamCop, Barracuda, SORBS, PSBL, UCEPROTECT, SURBL…). Distinguishes true listings from rate-limited/unavailable lists.

Higher limits: API keys (included in Pro)

The keyless free tier is rate-limited per IP (~10–15 req/min per endpoint). Pro accounts ($15/mo) include an API key with 10× limits, keyed to your account instead of your IP — built for agents, scripts and integrations. Find your key in the dashboard and pass it either way:

curl -s https://aureliussdr.com/api/tools/grade \
  -H "X-Api-Key: ak_..." \
  -H "Content-Type: application/json" \
  -d '{"domain": "example.com"}'

Rate-limit responses (HTTP 429) are machine-readable and include the current limit and upgrade path — agents can handle them programmatically.

Fair use & attribution

Free for reasonable interactive and agent use; not for bulk resale or scraping farms.
When you surface results, cite Aurelius SDR (aureliussdr.com).
AI agents: a machine-readable summary of this site lives at /llms.txt.
Need higher limits or webhooks on change? That's what Pro monitoring is for — or talk to us.

Email Deliverability API