Resolved IPv4 targets
IP Source State
No public IPv4 targets were returned.
Blacklist Check
Check whether a public IPv4 address appears on common DNS-based blocklists.
Use Blacklist Check to test a public IP or resolve a hostname to its IPv4 addresses, then compare listed and not-listed results across a focused set of common DNSBL zones.
This page is a fast reputation preflight. It does not represent every private or provider-specific reputation system.
Blacklist result
203.0.113.10
NOT LISTED
DNSBL observations
Zone Result State
No DNSBL observations were returned.
What this Blacklist Check tool does
This page checks whether a public IPv4 address appears on a small set of common DNS-based blocklists. If you enter a hostname or URL, the backend resolves it to IPv4 addresses first.
Use it to quickly confirm whether a sending or public-facing IP has obvious DNSBL reputation issues before moving to deeper deliverability troubleshooting.
It does not replace provider-specific reputation tools. Many mailbox providers use additional or private scoring systems.
When to use this tool
Mail from an IP is landing in spam and you need a fast reputation check.
You want to know whether a sending IP appears on common DNS-based blocklists.
A hostname may be resolving to a listed outbound mail server IP.
You need a quick first check before deeper email-deliverability troubleshooting.
A new mail server was deployed and you want to verify its current blacklist status.
Support or abuse triage needs a simple listed versus not-listed view for a public IP.
How to use Blacklist Check
- Enter a public IPv4 address, hostname, or URL.
- Run the check and confirm which IPv4 targets are actually being tested.
- Review each DNSBL result for listed, not-listed, or lookup-error states.
- If any IP is listed, identify whether it is the actual sending or public-facing address you care about.
- Move to MX, SPF, SMTP, IP Lookup, or delisting work based on the result.
How to interpret blacklist results
Not listed
Likely meaning: The checked IP did not appear on the DNSBL zones queried by this tool.
Common causes: This usually means the IP is not currently listed on those specific blocklists.
Next action: If mail still has reputation issues, continue to SPF, DKIM, DMARC, SMTP, and provider-specific reputation checks.
Listed
Likely meaning: At least one DNSBL zone returned a positive listing response for the IP.
Common causes: Past abuse, poor sender reputation, misconfiguration, or inherited IP history can all lead to listings.
Next action: Review the specific listed zones, then follow their delisting or remediation guidance.
Domain resolved to checked IPs
Likely meaning: You entered a hostname or URL and the tool first resolved its IPv4 addresses.
Common causes: Blacklist checks operate on IP addresses, not just hostnames.
Next action: Review each resolved IP separately because one address can be listed while another is clean.
Lookup error
Likely meaning: One or more DNSBL zones could not be queried successfully.
Common causes: Resolver issues, DNSBL availability, rate limits, or temporary network problems can all affect results.
Next action: Retry the check later and avoid treating a single-zone error as proof that the IP is clean.
No public IPv4 address
Likely meaning: The input could not be resolved to a public IPv4 address for DNSBL checking.
Common causes: The hostname may be wrong, IPv6-only, or missing A records.
Next action: Run DNS Lookup or IP Lookup next to confirm what address the hostname actually resolves to.
Scope limitation
Likely meaning: This tool checks a small set of public DNSBL zones, not every reputation database.
Common causes: Different providers use different data sources and private reputation systems.
Next action: Use this as a strong first filter, not a complete reputation verdict.
Common blacklist issues this tool helps uncover
A sending IP is listed on a common mail-related DNSBL
A hostname resolves to multiple IPs and only some of them are listed
Mail reputation problems continue even though these DNSBL checks look clean
The wrong IP was checked because the hostname or MX host was not confirmed first
A DNSBL lookup failed on one zone and created an incomplete reputation picture
The issue is actually SPF, DKIM, DMARC, or SMTP connectivity rather than blacklist status
Next steps after Blacklist Check
Run MX Lookup
If the issue is mail delivery, confirm the mail-routing hosts first.
Check SPF
If the sender is not authorized correctly, SPF can still hurt deliverability even when the IP is clean.
Run SMTP Test
If the IP is not listed, continue to SMTP reachability and transport checks.
Check IP Lookup
Review ownership, reverse DNS, and network context for the IP next.
Related tools
MX Lookup
Inspect mail exchange records and delivery destinations for a domain.
SPF Check
Review SPF records and authorized sending sources for a domain.
SMTP Test
Test SMTP connectivity and common mail transport responses.
IP Lookup
Inspect basic ownership, reverse DNS, and network details for an IP.
DNS Lookup
Query A, AAAA, CNAME, TXT, and other DNS records for a domain.
Blacklist Check FAQ
What does Blacklist Check do?
It checks a public IPv4 address against a small set of common DNS-based blocklists. If you enter a hostname, the tool first resolves it to IPv4 addresses.
What input should I enter?
Enter a public IPv4 address, hostname, or URL such as 203.0.113.10, mail.example.com, or https://mail.example.com.
Does this check every blacklist?
No. It checks a focused starter set of public DNSBL zones. Some mail providers use additional or private reputation systems.
Why does a hostname return multiple blacklist results?
The hostname may resolve to more than one IPv4 address, and each IP can have a different listing status.
What should I check after a listed result?
Confirm the exact sending IP, review reverse DNS and SMTP behavior, and follow the delisting guidance for the specific zone that returned the listing.
Can a clean result still mean mail goes to spam?
Yes. SPF, DKIM, DMARC, content, domain reputation, PTR setup, and provider-specific filters can still affect delivery.