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how.is Domain Blacklist Check
x402
how.is Domain Blacklist Check is a paid API for AI agents from how.is, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-31).
Checks whether the IP addresses behind a domain appear on spam and abuse blocklists.
Price / call$0.005
Success—
StatusUnknown
How this service works
Whether the addresses behind a domain appear on spam and abuse blocklists.
Output
Returns a JSON object with per-IP results for the queried domain, including whether each IP is listed on any blocklist, how many lists it appears on, and how many total blocklists were checked. Also includes a receipt with payment metadata.
Example use cases
Email deliverability pre-send check
“Before we send our newsletter campaign, can you check if our sending domain mailouts.acme.com is showing up on any spam or abuse blocklists?”
Vetting a third-party vendor domain
“We're about to integrate with a partner at partnerhub.io — can you check if their domain's IPs are blacklisted on any abuse lists before we proceed?”
Investigating suspicious inbound email
“I got a sketchy email from someone at bargainpharmacy.ru — can you check if that domain is on any spam or abuse blocklists?”
Technical details
Endpoint
POSThttps://how.is/v1/domain/blacklist?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to check whether a specific domain's underlying IP addresses are flagged on known spam and abuse blocklists. Ideal for email deliverability verification, security vetting of third-party domains, or investigating suspicious senders. Prefer this over generic WHOIS or DNS lookups when the specific question is about blacklist/blocklist reputation rather than ownership or DNS records.
Side effects
- Invalid or malformed domain name returns an error
- Domain with no resolvable IPs may return empty or null IP results
- Rate limiting or payment failure may prevent the call from completing
- Domain may have IPs not yet indexed by blocklist providers, leading to incomplete results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| domain | string | A bare domain name, e.g. example.com |
Output
Schema · Response
{
"type": "json",
"example": {
"data": {
"_shape": "data.data.ipResults[]: target, isListed, listingCount, totalChecked."
},
"result": "Blacklist status for the requested subject",
"receipt": {
"rail": "x402",
"tool": "blacklist",
"charge_usd": 0.005,
"settlement_tx": "0x…"
}
}
}Tags
x402
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