Blacklist Checker

A DNS blocklist — also called a DNSBL or RBL (real-time blackhole list) — is a published list of IP addresses with a bad sending reputation distributed over DNS so any mail server can query it instantly. When a message arrives the receiving server looks up the sender's IP on one or more of these lists. A hit means the mail is likely to be rejected or filtered to spam. IPs land on blocklists for sending spam relaying mail openly being part of a botnet or generating a spike of complaints. Sometimes a shared hosting IP is listed because of a neighbour's behaviour which is why checking your own IP matters even if you've done nothing wrong.

First find and fix the cause. Common culprits are a compromised mailbox sending spam a misconfigured server acting as an open relay or a marketing send that triggered complaints. Listing you again right after delisting is worse than staying listed so resolve the root issue first. Then request removal directly from the listing provider — each runs its own delisting form and most will remove a clean IP within hours to a few days. Keep your authentication tight (SPF DKIM DMARC) warm up new IPs gradually and monitor your reputation so you catch the next listing early rather than after deliverability has already dropped.

It resolves your domain's IP address and queries it against a set of well-known public DNS blocklists (DNSBLs) — the same lists mail servers and spam filters consult. You instantly see which lists you're clean on and which (if any) have you listed so you can tell whether a deliverability problem is a reputation issue.

Mail servers and spam filters check sender IPs against DNSBLs in real time. If your sending IP is listed your email is far more likely to be rejected outright or dropped into spam — even if your SPF DKIM and DMARC are perfect. Blocklist hits are one of the most common hidden causes of my email isn't arriving.

Each blocklist runs its own delisting process. First fix the root cause (a compromised account an open relay or a spam complaint spike) then visit the listing provider's site and submit a removal request for your IP. Removal can take anywhere from minutes to several days. Re-run this check afterward to confirm.

It checks the IP address your domain currently resolves to (its A record). Most DNSBLs operate on IP addresses so that's what matters for mail reputation. If your domain has no A record there's no IP to check and we'll tell you so.

Yes — every blocklist is queried live via DNS at the moment you run the check with no server-side caching. Results reflect the current state of each list.