Blocklist Checker

A DNS blocklist, or DNSBL, is a published list of IP addresses (and sometimes domains) that have been seen sending spam or abusive mail. Receiving mail servers query these lists in real time and use a listing as a signal to reject, defer, or spam-folder your message. They are also called RBLs (Realtime Blackhole Lists) or blacklists.

Enter your sending IP address (or a domain, which we resolve to its IP) above and run the check. The tool queries several major blocklists at once and shows whether the address is listed on each, along with a delisting link for any list that has it. For the most accurate result, check the exact IP your mail actually leaves from — for most senders that is your email provider's or ESP's outbound IP, not your website's IP.

Several large operators, including Spamhaus and Barracuda, only answer blocklist queries that come from a dedicated, registered resolver. Queries from a large shared resolver (like the one a hosted app uses) are answered with an error code instead of a real result. When we detect that, we show 'Can't check' and link to the operator's own lookup page so you can confirm directly, rather than reporting a false 'not listed'.

The most common causes are: spam or unsolicited mail sent from the IP (sometimes by a compromised account or device on the same network), hitting spamtraps from an old or purchased list, a poor sending reputation from high complaint or bounce rates, missing or generic reverse DNS (PTR), and shared-IP problems where another sender on the same address caused the listing. Fixing the root cause matters more than the delisting itself.

First fix what caused the listing — secure any compromised accounts, clean your list, and make sure your mail is authenticated with SPF, DKIM, and DMARC. Then use the operator's delisting form (linked next to each listing above). Many lists, such as SpamCop, expire entries automatically once the abuse stops, so patience plus a fixed root cause is often enough. Requesting delisting without fixing the cause almost always leads to a re-listing.

Not always. Some lists are consulted by almost every receiver (Spamhaus is the most influential), while others are used by only a handful of servers or are purely advisory. A listing on a widely used list can cause outright rejections; a listing on a niche list may only nudge you toward the spam folder. The checker shows every list separately so you can judge the impact by which list has you.

Most blocklists are IP-based, so the sending IP is what matters for delivery. If you enter a domain, we resolve it to an A record and check that IP — but note that is often your website's host, not the server that sends your email. To diagnose a delivery problem, look at your bounce message or email headers to find the real outbound IP and check that.