IP Blacklist Check API: Flag a Listed Address
An IP blacklist check API tells you whether an address appears on major email/IP blocklists before you accept a signup or send mail. On ipXapi that is GET https://ipxapi.com/api/blacklist-check?ip= with Authorization: Bearer. The documented example IP is 8.8.8.8 (IPv4 required).
Basic is $29.99/mo with a 7-day trial or 50 requests. This is not GET /api/ip (city/ASN) and not /api/fraud-score. MCP: https://mcp.ipxapi.com (the path ipxapi.com/mcp 404s). Docs: quick-start on ipxapi.com.
Request: check 8.8.8.8
curl 'https://ipxapi.com/api/blacklist-check?ip=8.8.8.8' \
-H 'Accept: application/json' \
-H 'Authorization: Bearer YOUR_KEY'
Response fields (product fixture)
Feature tests cache this 8.8.8.8 envelope. Live is_listed can change — copy the curl with your key.
{
"ip": "8.8.8.8",
"is_listed": false,
"checked_blacklists": 100,
"listed_count": 0,
"ok_count": 100,
"timeout_count": 0,
"listed_blacklists": [],
"timeouts": []
}
When listed, listed_blacklists[] includes name, status, and reason. Missing ip returns 400 missing_parameter; a bad address returns 400 invalid_ip.
PHP: gate a signup
$ch = curl_init('https://ipxapi.com/api/blacklist-check?ip=' . urlencode($ip));
curl_setopt_array($ch, [
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => [
'Accept: application/json',
'Authorization: Bearer YOUR_KEY',
],
]);
$data = json_decode(curl_exec($ch), true);
curl_close($ch);
if (!empty($data['is_listed'])) {
// hold the account for review
}
Go live
1. Register — 7-day trial or 50 requests.
2. Copy the Bearer token.
3. GET /api/blacklist-check?ip=.
4. Branch on is_listed.
Check a blacklist with an ipXapi key →