--- title: Free Blacklist Check description: Check an IPv4 address against the Spamhaus ZEN, SpamCop and Barracuda blocklists (a domain is checked through the address it resolves to). canonical: https://watchfor.io/blacklist-checker --- [Back to all free tools](/free-tools) # Blacklist Check Check an IPv4 address against the Spamhaus ZEN, SpamCop and Barracuda blocklists (a domain is checked through the address it resolves to). [How to use this tool](/blog/how-to-check-if-your-ip-is-blacklisted) Result No result yet Fill in the form above and run it — the result appears here. Monitor this 24/7 — get alerted when a failure is confirmed. [Start free](/auth/sign-up) Only run these tools against systems you own or are authorized to test. Using them to scan or probe systems without permission violates our [Terms](/legal/terms). ## What is Blacklist Check ? DNS-based blocklists (DNSBLs, often called RBLs — Real-time Blackhole Lists) are queryable databases of IP addresses known for sending spam or hosting abuse. When your mail server tries to deliver to a receiver and gets rejected with 554 5.7.1 Service unavailable; Client host blocked using Spamhaus , the receiver looked your sending IP up in a blocklist and found it. Receivers use these listings as one of several reputation signals, so a listing can mean bounces, or mail quietly landing in spam. This tool checks an IPv4 address against the blocklists most mail servers consult — Spamhaus ZEN , SpamCop and Barracuda — in parallel, and shows listed or clean for each, with the query time. Enter the IP of the server that sends your mail. If you enter a domain, the tool resolves it and checks the first address it gets, which is usually the website, not the mail server. ## How it works DNSBL queries are DNS lookups in disguise: - 1 Resolve the target to an IPv4 address — An IP is used as is. A hostname is resolved and its first address is checked. IPv6 addresses aren't supported yet. - 2 Reverse the IP and query each list — For 1.2.3.4 the probe asks for the A record of 4.3.2.1.zen.spamhaus.org , 4.3.2.1.bl.spamcop.net and 4.3.2.1.b.barracudacentral.org , all at once. - 3 Read the answer — No such name means not listed. A 127.0.0.x answer means listed. Spamhaus answers 127.255.255.x when it refuses a query (for example from a public resolver); that shows as refused , not as a listing. The queries go through the probe's own resolver, not a public one like 1.1.1.1 or 8.8.8.8 , because Spamhaus refuses queries from large public resolvers. Lookups are read-only; querying a DNSBL is exactly what it is built for. ## When you'd use it ### "My mail is bouncing — am I blacklisted?" Recipients reject your mail and the bounce names a blocklist. Check your sending IP here. If a list shows listed , open that list's own lookup page (Spamhaus's check.spamhaus.org , SpamCop's and Barracuda's lookup pages) to see the reason and the delisting steps. ### Bought a new IP from a hosting provider Cloud providers recycle IPs. The one you just got might have been used by a spammer a week ago and still carry their listing. Check fresh IPs before sending real mail from them. ### Periodic deliverability check Even legitimate senders get listed occasionally: shared infrastructure, a compromised account, a customer sending junk through you. A regular check catches a listing before it shows up as delivery failures. ### Investigating an abuse complaint A recipient ISP complains about spam from your IP. Check whether the big lists agree. The listing's reason on the list's own site often names the pattern and the time it was seen, which helps you find the account or host that caused it. ## Reading the result ### Listed / clean One row per blocklist. Listed means the list has your IP. Clean means it doesn't. The tool doesn't decode the listing's reason or show removal links; the list's own lookup page has both. ### Timeout, refused, error The list didn't give a usable answer, so the row says nothing about your IP either way. Run it again; a persistent refused from Spamhaus means it is refusing our resolver, not that you are listed. ### Why Spamhaus matters most Spamhaus ZEN combines its SBL (spam sources), XBL (compromised hosts, exploits) and PBL (address space that shouldn't send mail directly) lists, and most large mail providers consult it. A Spamhaus listing is the one to fix first. Its lookup page tells you which of the three lists you are on, and getting off the PBL is a different process from getting off the SBL. ### Query time How long each list took to answer, in milliseconds. It tells you about the list's DNS servers, not about your reputation. ## Common pitfalls ### Checking the website instead of the mail server Typing example.com checks the address the domain itself resolves to, which is normally the web server or CDN. Mail usually leaves from another IP: look up your MX host or your mail provider's sending IPs, or read the IP from the Received header of a sent message, and check that. ### "I'm listed but I'm not sending spam — what now?" Three usual reasons: (1) shared IP space — the provider's range is listed because of someone else; (2) a compromised host or account relayed spam without your knowledge — check the logs; (3) a PBL listing — the IP is in dynamic or residential space that shouldn't send mail directly; send through a proper mail server or relay. ### Mail rejected but every list shows clean Not all filtering is blocklist-based. Gmail and Microsoft use their own reputation systems that never appear in public lists. Check Google Postmaster Tools and Microsoft SNDS, and check SPF, DKIM and DMARC. ### Removed from a list but mail still bouncing Receiving servers cache DNS answers, including the listing, for the list's TTL. After delisting, some receivers keep the old answer for a while. Wait it out or contact the receiver's postmaster. ## Run Blacklist Check on every change, not just once. Get alerted when an outage is confirmed — across HTTP, DNS, SSL, RDAP, ping, blacklist and more. Free forever for 15 monitors. No card. [Start free](/auth/sign-up) ## Frequently asked questions Which blocklists does this tool check? Spamhaus ZEN, SpamCop and Barracuda — the IP lists most mail servers consult. It doesn't check domain (URI) blocklists such as SURBL or URIBL, or the long tail of smaller lists. How do I get removed from a blocklist? Fix the cause first (close open relays, lock compromised accounts, stop the unwanted mail). Then use the delisting process on the list's own site: Spamhaus through check.spamhaus.org , SpamCop listings expire on their own once the reports stop, and Barracuda has a removal request form. This tool shows whether you are listed; it doesn't submit removal requests. Can I check a domain? You can type one, but the tool resolves it and checks its first IPv4 address, which is usually the web server. That answers "is this server listed", not "is this domain listed". For mail, check the IP your mail is sent from. Does it support IPv6? Not yet. IPv6 addresses are rejected with a message, and a hostname is checked through its IPv4 address. Will being on one blocklist hurt my mail deliverability? It depends on the list and the receiver. A Spamhaus listing has the widest effect because most large providers consult it. Receivers weigh many signals, so one listing usually hurts but rarely blocks everything. Can I be blocklisted for sending too much legitimate mail? Yes. High-volume senders without SPF, DKIM and DMARC, or with poor list hygiene (unverified addresses, ignored unsubscribes), can trigger listings. Volume itself isn't the problem; volume plus signs of unwanted mail is. How often should I check my IPs? Daily for servers that send production mail. Listings can appear within minutes of a spam run, and catching them early means you start delisting before receivers notice. A blacklist monitor runs the same check on a schedule and alerts you when a list changes. ## Related network tools - [PingICMP echo request — round-trip time, jitter, packet loss.](/ping-test) - [TracerouteTrace the network path hop by hop, with packet loss and average latency at each hop (MTR-style).](/traceroute-online) - [Port CheckerTest TCP port reachability and optionally grab the server banner.](/port-checker) - [What Is My IPSee your public IPv4 / IPv6 address, approximate location (city, region, country), timezone and map coordinates — detected instantly from your connection, no signup.](/whats-my-ip) --- Canonical page: https://watchfor.io/blacklist-checker · Site guide: https://watchfor.io/llms.txt