DNS Blocklist Check
Check an IPv4 address against four major public DNS blocklists (Barracuda, SpamCop, SORBS, DroneBL). A listing means the IP sent spam or abuse — mail sent from it will bounce or junk across the internet. The pre-flight check before sending email from any server or relay.
🔌 Server-side tool
This tool runs on the server (it fetches third-party URLs directly and cannot run in your browser). Use the paid JSON API below — the worked examples show real server-side results and refresh automatically.
Worked examples
Google DNS
GET /api/v1/security/dnsbl-check?ip=8.8.8.8
Result: ✓ 8.8.8.8 is clean — not listed on 4/4 reachable blocklists
A documentation IP
GET /api/v1/security/dnsbl-check?ip=203.0.113.5
Result: ✓ 203.0.113.5 is clean — not listed on 4/4 reachable blocklists
Cloudflare
GET /api/v1/security/dnsbl-check?ip=1.1.1.1
Result: ✓ 1.1.1.1 is clean — not listed on 4/4 reachable blocklists
Machine API (x402)
$0.02 / callThis tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.
GET /api/v1/security/dnsbl-check?ip=8.8.8.8 HTTP/1.1
Host: agentstoolshub.com
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "security/dnsbl-check",
"input": {"ip":"8.8.8.8"},
"result": { "value": 0, "answer": "✓ 8.8.8.8 is clean — not listed on 4/4 reachable blocklists" }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
Queries the major public DNS blocklists for an IPv4 address and reports a per-list verdict. Newly rented servers are frequently pre-listed by a predecessor's spam — checking before configuring mail (or trusting a partner's server) saves days of deliverability pain.
Frequently asked questions
Why isn't Spamhaus included?
Spamhaus blocks queries from shared public resolvers (like the DoH endpoint used here), which would make results unreliable. The four lists included all accept shared-resolver queries and cover the bulk of receiver-side filtering.
How do I get delisted?
Each blocklist has its own removal process (usually a web form once the root cause is fixed). Listings auto-expire in days-to-weeks after the abuse stops — fix the sending problem first.