Comprehensive Blacklist Lookup
Check your IP or Domain against 40+ public blacklist and reputation sources. Diagnose email deliverability issues and monitor your IP reputation.
What is a Blacklist Lookup?
A diagnostic scan that checks if your mail server's IP address is listed on DNS-based Blackhole Lists (DNSBLs) or reputation databases used by many mail systems when evaluating incoming mail.
Monitoring Deliverability
Email servers can query DNSBLs when evaluating whether to accept, reject, or flag incoming email. A listing on a public blacklist may affect delivery to some receiving systems, depending on their filtering policies.
Diagnosing Rejection
When users report that your emails are bouncing with "550 5.7.1 Service unavailable" errors, a blacklist lookup can be a useful first diagnostic step. It identifies exactly which security databases have flagged your IP, allowing you to target your delisting requests accurately.
Shared IP Risks
On shared hosting or cloud environments, activity from other senders sharing the same IP can affect the IP's reputation and delivery performance. Regular monitoring can help you catch reputation issues early and request a dedicated IP from your provider if necessary.
Real-Time Server-Sent Events (SSE)
Results are streamed progressively using Server-Sent Events (SSE), allowing completed checks to appear without waiting for the entire scan to finish. Watch completed checks appear live without reloading the page.
Blacklist Checker Tool
Types of Blacklists and Reputation Sources
Understanding the different categories of reputation systems and what they specifically monitor.
| Category | Primary Focus | Notable Examples |
|---|---|---|
| Spam Traps | Lists IPs that send emails to hidden "trap" addresses or known spam sources. | Spamhaus ZEN, Spamcop BL |
| Botnet / Compromised | Identifies servers hijacked by malware or botnets to send bulk spam. | Barracuda RBL, DroneBL |
| Dynamic / End-User | Blocks residential or dynamic IPs (DSL/Cable) from sending direct SMTP mail. | Spamhaus PBL, UCEPROTECT |
| Phishing / Malware | Flags IPs and domains hosting malicious payloads or phishing campaigns. | GreenSnow, Anti-Attacks |
| Domain-Based (SURBL) | Blacklists domains found inside the body of spam emails, rather than the sending IP. | SURBL Multi, URIBL |
Understanding IP Reputation
Key technical concepts behind how email providers evaluate your server's trustworthiness.
DNSBL vs. RBL
DNSBL and RBL are commonly used terms for DNS-based reputation/blocklists, although the terminology and list implementations can differ. Historically, RBL is the older legacy term coined in the 1990s.
IP vs. Domain Reputation
Blacklists primarily track IP addresses. However, modern filters (like Gmail) also track Domain Reputation via DMARC alignment. A clean IP won't save you if your domain lacks proper SPF/DKIM authentication.
The Delisting Process
Removal is rarely automatic. You must first resolve the underlying issue (e.g., secure a compromised server), then visit the specific blacklist operator's site to submit a delisting request. Repeated or unresolved abuse can make delisting more difficult, depending on the blacklist's policy.
Reverse DNS (PTR)
Many public blacklists and receiving servers require a valid PTR record (Reverse DNS) that matches your hostname. If your IP resolves to a generic ISP name instead of your mail server's FQDN, it may reduce deliverability or cause rejection by some receiving systems.
Honest by Design — What This Tool Does
This tool uses live DNS queries to audit your server safely. Here is exactly what it does and doesn't do:
- Streams results live via Server-Sent Events (SSE).
- Resolves domains to IPs automatically via server-side DNS.
- Queries 40+ public reputation sources.
- We do not intentionally store submitted IP addresses or domains in this tool's application data.
- Does NOT submit delisting requests or fix server configuration issues automatically.
- Does NOT guarantee inbox placement (requires SPF/DKIM/DMARC).
This tool does
- Perform real-time public DNS queries
- Resolve domains to IPv4 addresses
- Stream results without page reloads
- Export full reports to CSV
- Identify checked databases that list the IP
This tool does not
- Intentionally store your IP history in application tables
- Submit delisting requests for you
- Check private / enterprise blocklists
- Verify SPF, DKIM, or DMARC records
- Guarantee inbox placement at Gmail, Outlook, or other providers
- Require an account or login
How to Use This Checker
Four steps to audit your mail server's IP reputation.
Enter Target
Input the domain name or IPv4 address of the mail server you want to audit.
Stream Scan
Click check. Our server resolves the IP and queries 40+ public reputation sources, streaming results live.
Review Status
Identify any red "Listed" cards. These are the checked databases that currently list your IP.
Export & Fix
Download the CSV report and visit the listed blacklist websites to follow their delisting procedures.
Deliverability Pitfalls
Avoid these critical errors when managing mail server reputation and blacklists.
Spamming Delisting Requests
Submitting dozens of automated delisting forms without fixing the underlying spam vulnerability.
Fix: Delisting procedures vary by blacklist, and repeated requests may be restricted or reviewed more closely. Always resolve the security issue first.
Ignoring Shared IP Reputation
Assuming your clean sending practices protect you on a shared hosting environment.
Fix: Activity from other senders sharing the same IP can affect the IP's reputation and delivery performance. For critical mail, use a dedicated IP or trusted SMTP relay.
Missing Email Authentication
Having a clean IP blacklist report but still landing in spam folders.
Fix: Blacklists only check reputation. Major providers increasingly require or strongly recommend email authentication such as SPF, DKIM, and DMARC, depending on sender type and volume.
Ignoring Dynamic IP Lists
Panicking because your IP is listed on the Spamhaus PBL or UCEPROTECT.
Fix: These specific lists block residential/dynamic IPs from sending direct SMTP mail. A PBL listing is a policy classification, not necessarily an indication that the IP has sent spam. Route mail through your ISP's relay.
Missing Reverse DNS (PTR)
Being rejected by strict enterprise mail servers despite having a clean blacklist report.
Fix: Receiving servers verify that your IP resolves back to your hostname via a PTR record. Ensure your hosting provider configures a valid Reverse DNS entry that matches your mail server's FQDN.
Assuming "Not Listed" = Inbox
Believing that passing 40+ reputation checks guarantees your marketing or transactional emails will hit the primary inbox.
Fix: Blacklists only catch known issues. Inbox placement is heavily dictated by user engagement (open/click rates), content quality, and domain reputation. Monitor your Google Postmaster Tools dashboard.
Blacklist Checker vs. Other Mail Tools
Which diagnostic tool should you use for your current email deliverability issue?
Who Uses Blacklist Checkers?
High-impact scenarios for auditing mail server reputation and diagnosing deliverability.
Email Deliverability Troubleshooting
When users report missing transactional emails or newsletters going to spam, this can be a useful diagnostic step to see if the sending IP has been globally flagged.
New Server & IP Auditing
Before launching a new mail server or migrating to a new cloud provider, verify the assigned IP isn't already blacklisted from a previous tenant's spam activities.
Post-Incident Forensics
After a WordPress site is hacked and used to send spam, sysadmins use this tool to verify the cleanup was successful and track the delisting progress across all major databases.
SMTP Relay Monitoring
DevOps teams managing outbound mail relays use automated blacklist checks to catch reputation degradation early, before enterprise clients start complaining about bounced invoices.
Agency Client Reporting
Marketing agencies include blacklist status in deliverability reports as one reputation-related check to monitor their outbound infrastructure.
Network Security Teams
Security analysts check outbound IPs to identify internal botnet infections or compromised workstations that are silently beaconing to command-and-control servers.
Blacklist Checker FAQs
Straight answers about DNSBLs, IP reputation, and email deliverability.
What is a DNSBL?
DNSBL stands for DNS-based Blackhole List. It is a DNS-accessible list of IP addresses associated with spam, abuse, or other reputation-related activity, depending on the list's purpose. Receiving mail servers query these lists via DNS to decide whether to accept or reject incoming mail.
Is this tool free and private?
Yes, 100% free. The scan uses public DNS-based reputation data and does not require an account. We do not intentionally log or store the IPs or domains in our application database.
My IP is clean, but emails still go to spam. Why?
Blacklists only catch known bad IPs. Modern inbox placement relies heavily on SPF, DKIM, and DMARC authentication, domain reputation, and user engagement (open/click rates). Use a DNS Lookup tool to verify your authentication records.
What should I do if my IP is listed?
First, identify and fix the root cause (e.g., secure a hacked WordPress site or close an open SMTP relay). Then, visit the specific DNSBL's website and follow their manual delisting procedure. Do not submit requests until the vulnerability is patched.
Why am I listed on Spamhaus PBL?
The PBL (Policy Block List) is a database of dynamic/end-user IP ranges (like residential ISPs) that should not be sending direct SMTP mail. A PBL listing is a policy classification, not necessarily an indication that the IP has sent spam. Route mail through your ISP's relay.
Does this tool check IPv6 addresses?
Currently, this version of the tool supports IPv4-based DNSBL queries. Support for IPv6 DNSBL queries is on our development roadmap.
Can I export the results?
Yes. Once the live scan completes, a Download CSV button appears, allowing you to export the report of all 40+ databases and their statuses to share with your hosting provider or IT team.
How often should I check my IP?
For high-volume mail servers, we recommend checking weekly. For larger mail operations, consider using an established monitoring system or API-based monitoring service.