IP/Domain Blacklist Checker
Enter an IP address or domain to check it against several major public DNSBL (DNS-based blackhole list) services - the same lists mail servers consult to decide whether to reject email as spam.
الأسئلة الشائعة
Which blacklists does this check?
Spamhaus ZEN, Barracuda Reputation Block List, SpamCop, CBL (Composite Blocking List) and PSBL for IP addresses, plus Spamhaus DBL for domains. These were chosen because each one reliably answers standard DNS-based lookups without requiring an account or API key. Other well-known lists, like SORBS, were left out after testing showed unreliable responses to standard test queries.
How does a DNSBL lookup actually work?
It's a plain DNS query: an IP's octets are reversed and looked up as a subdomain of the list's zone (checking 203.0.113.42 against Spamhaus means querying 42.113.0.203.zen.spamhaus.org). If the list has an entry, the lookup returns an address (usually starting 127.0.0.x); if not, it returns "no such domain". This is the same mechanism every mail server uses in real time.
My IP is listed - what does that mean?
It means one of these providers has flagged that IP as a spam source at some point, which can cause mail sent from it to be rejected or sent to spam. Each list publishes its own delisting process; a shared IP (common on cloud hosting) can also get listed because of another customer's activity, not necessarily yours.
Does this tool send any email?
No, this only performs read-only DNS lookups against public blacklist zones. Nothing is sent, and no account or registration is required to use it.