What Blacklist Checker does
The Blacklist Checker accepts a public domain or IPv4 address. When you enter a domain, PagesTools resolves it to an IPv4 address and submits the reversed address to Spamhaus ZEN, SpamCop, Barracuda Central, and SORBS DNSBL lookups. Each provider is reported independently instead of being collapsed into a vague pass or fail.
A listing can help explain a mail-delivery problem, but it is only one diagnostic signal. Different mail systems use different reputation sources, and a provider may time out or return an inconclusive response. Read the zone-by-zone status alongside your mail logs, authentication records, and the receiving provider's rejection message.
How to use Blacklist Checker
- Enter a public domain name or IPv4 address; IPv6 is not supported by the selected DNSBL providers.
- Select Check blacklists and wait for the four DNS lookups to finish.
- Review the resolved IPv4 address and each provider's listed, not-listed, or unknown status.
- Investigate any listing with that provider directly before changing DNS or requesting delisting.
Important details
What the three statuses mean
Listed means a DNSBL returned an address for the query. Not listed means that provider returned no listing at the time of the check. Unknown means the provider lookup failed or could not be interpreted, so it should not be counted as a clean result.
Domain checks use one IPv4 address
A domain can resolve to several addresses. This check uses the first public IPv4 result exposed by the resolver, so repeat the check with each relevant sending IP when a mail system has multiple outbound servers.
Delivery requires more than a clear DNSBL report
Inbox placement also depends on message content, complaint history, IP and domain reputation, SPF, DKIM, DMARC, reverse DNS, and receiving-provider policy. A zero-listing result is not an email-delivery guarantee.
Practical uses
- Triage an SMTP rejection that mentions an IP reputation or blocklist problem.
- Check a newly assigned mail-server IPv4 address before production use.
- Record a point-in-time DNSBL snapshot while investigating delivery changes.
Privacy and limitations
The target is sent to the PagesTools server, which performs DNS resolution and DNSBL queries. Those DNS providers can observe the queried reversed IP, and the JSON response is returned with no-store cache headers.
The check covers four providers and IPv4 only. DNSBL data changes, provider outages can produce unknown results, and a listing or clear response does not predict how every recipient will handle mail.