Free JSON endpoints for SPF, DKIM, DMARC, MX and blacklist checks on any domain. No API key, no signup. Built for developers, scripts, and AI agents.
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.
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 }
}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.
DMARC record from _dmarc.<domain>, parsed tags (p, sp, rua, pct…), policy-strength issues and warnings.
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.
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.
Interactive versions: Domain Grader · SPF Checker · DMARC Checker · DKIM Checker · Blacklist Checker