IP address blacklist check: what each result means
A DNS-based blocklist, often called a DNSBL, lets a mail system check whether an IP address appears in a database run by a list operator. This page reverses the four IPv4 octets and checks 17 public DNSBL zones: Mailspike, PSBL, SpamCop, DroneBL, UCEPROTECT Level 1, s5h.net, Kempt.net, Backscatterer, UCEPROTECT Level 2, UCEPROTECT Level 3, Hostkarma, Fabel Spamsources, Schulte RBL, NoSolicitado, ZapBL, SPFBL, and blocklist.de. It checks only these lists, not every blacklist. Results are grouped by purpose into Spam sources, Bots, proxies and attacks, and Reputation and backscatter. Each list uses its own data, detection methods, and removal rules. A result tells you what those operators returned at query time; it cannot predict whether a recipient will accept a message.
Each list has one of three results. Listed means the DNS query returned a record in that list's zone. Not listed means the query completed and returned no address record. Couldn't check means the resolver failed or the lookup exceeded the endpoint's short overall time budget. A timeout or resolver policy can block a result, so it does not mean the address is clean. Each list name links to the operator's lookup or removal page for its explanation and current status.
Why an IP address might appear on a blacklist
Blocklists may record direct spam sources, compromised devices, suspicious activity, or address ranges that should not send mail directly to receiving servers. Carrier-grade NAT can put many customers behind one public IP, and providers may reassign an address to someone else. Mailspike classifies reputation levels. UCEPROTECT Level 1 is intended to identify an individual IPv4 address, while Levels 2 and 3 list whole provider ranges or networks. Those broader listings can affect customers who sent nothing. Hostkarma's whitelist and mixed answers are reported as not listed. Each list has its own criteria and update cycle. A listing alone does not prove that you sent unwanted mail.
Residential internet addresses are often expected to send email through an authenticated provider or ISP relay, rather than connect directly to every recipient's mail server. A policy listing can be normal for the address shown by a home connection. If you operate a mail server, check its actual outbound address, mail logs, reverse DNS, SPF, DKIM, and DMARC before taking action. Your browser IP may differ from the server that sends your mail.
What to do after a blacklist IP lookup
Open the affected operator's page and follow its evidence and removal process. If a listing points to a shared provider range, contact your ISP or hosting company, since you may not control the address. For a dynamic home address, the provider may rotate it or offer a mail relay. Be wary of paid removal services that promise to erase a listing without checking the operator's rules. Our blacklist guide explains how a DNSBL result relates to mail delivery. The CGNAT guide covers shared public addresses.
Frequently asked questions
Does “listed” mean my email is blocked everywhere?
No. Mail providers choose which reputation sources to use and how strongly to weigh them. A listing can matter to one receiver and be ignored by another.
Can this IP blacklist lookup check IPv6?
Not yet. This tool checks IPv4 DNSBL zones only. Use an operator's own checker if it offers IPv6 support.
Why does a lookup say “couldn't check”?
The server's resolver may time out, restrict the query, or lack DNS lookup support. Retry later or use the linked list operator's checker.
Is my address stored?
The address is sent to the site's server and appears in the DNS query sent through the host's resolver to each list. The tool does not save a lookup history; ordinary hosting logs may apply.
More free tools: IP lookup · Port checker · WebRTC test · Speed test