Blacklist Checker — Is Your IP or Domain on a Spam Blacklist?

By sadiqbd · June 6, 2026

Landing on a spam blacklist is one of the quietest ways email deliverability fails

Your emails look fine. Your SPF, DKIM, and DMARC are all configured correctly. But your open rates have dropped, some recipients report not receiving your messages, and support tickets about "missing" emails keep coming in. One likely culprit: your sending IP or domain is on one or more spam blacklists.

A blacklist checker queries the major DNS-based blacklists (DNSBLs) in one shot and tells you immediately whether you're listed — and where.

What Spam Blacklists Are

Email spam blacklists (also called blocklists or DNSBLs — DNS-based Block Lists) are databases of IP addresses and domain names associated with spam, phishing, malware distribution, or other abusive email behaviour. Mail servers worldwide query these lists in real time during email delivery to decide whether to accept, quarantine, or reject incoming messages.

There are dozens of widely used blacklists:

Major IP-based lists:

Spamhaus ZEN — the most widely respected composite list, combining SBL (Spamhaus Block List), CSS (spammer IPs), XBL (exploited systems/malware), and PBL (Policy Block List for dynamic IPs)
Barracuda Reputation Block List (BRBL) — widely used by enterprise mail filters
SORBS — focuses on spam sources, open relays, and dynamic IPs
SpamCop — community-reported spam sources

Domain-based lists:

Spamhaus DBL — lists domains used in spam
SURBL — URIs found in spam message bodies
URIBL — URI reputation list

Why You Might Get Listed

Spam complaints. Recipients marking your email as spam triggers complaint reporting to feedback loops. High complaint rates (above 0.1% on most platforms) can lead to blacklisting.

Sending from a shared IP with bad neighbours. If you use shared sending infrastructure (many email marketing platforms use shared IPs), a heavy spammer on the same IP pool can drag your deliverability down.

Compromised server or account. If your server or an email account is hacked and used to send spam, the sending IP gets blacklisted quickly.

Cold outreach at high volume. Sending unsolicited cold emails at scale will generate complaints and blacklist hits, regardless of how "relevant" you think the email is.

Dynamic IP listing. Many residential and small business IP ranges are listed on PBL-type lists by default, since mail should come from dedicated email servers. If you're sending email from a home internet connection or small-office IP, it may be pre-listed on these policy lists.

Newly purchased or reused IP. IP addresses have reputation histories. A new IP or one that previously belonged to a spammer may inherit a bad reputation.

How to Use the Blacklist Checker on sadiqbd.com

Enter your IP address or domain — your sending IP (check your email headers to find it) or your domain name.
Run the check — the tool queries all major DNSBLs simultaneously.
Read the results — a summary of which lists you appear on (or confirming you're not listed).

For domains: check both the root domain (example.com) and any subdomains used in email (mail.example.com).

To find your sending IP:

Send yourself an email from your domain
View the full email headers
Look for Received: headers — the earliest one contains your outgoing mail server IP

Reading the Results

Not listed anywhere: Your IP/domain is clean on all checked lists. Deliverability problems, if present, are caused by something else (DMARC failures, content filtering, recipient engagement signals).

Listed on Spamhaus PBL: This is a policy listing for dynamic/residential IPs, not a spam complaint. It means you're trying to send email from an IP range not designated for direct mail delivery. Solution: use a proper email service provider (ESP) or dedicated mail server with a static IP.

Listed on Spamhaus SBL/CSS: More serious — indicates a spam report or manual review found spam activity from this IP. Requires investigation and a delisting request to Spamhaus after resolving the root cause.

Listed on Barracuda BRBL: Follow the delisting process at Barracuda's reputation portal. Usually requires submitting a delisting request and potentially waiting for reputation to recover.

Listed on SpamCop: SpamCop listings are time-limited (they expire after ~24–48 hours if no new spam is detected). If you were listed due to a temporary spike or a compromised account, the listing may clear on its own after the issue is resolved.

How to Get Removed from a Blacklist

Each blacklist has its own delisting process:

Spamhaus: Visit spamhaus.org and use their lookup tool. Listings include the reason and a link to request removal if you've resolved the issue. Automated removals are available for some list types; others require manual review.

Barracuda: Submit a removal request through Barracuda's reputation lookup portal at barracudacentral.org. Typically processed within 12–24 hours.

SpamCop: Time-limited listings usually expire automatically (24–48 hours) if no new spam activity continues. No manual delisting action needed in most cases.

SORBS: Contact SORBS with proof that the issue has been resolved. Some listings require payment for expedited removal (controversial but it's their policy).

Microsoft Smart Network Data Services (SNDS): For deliverability to Outlook/Hotmail addresses, register at Microsoft's SNDS portal to understand your sending reputation and submit delisting requests for their block list separately.

Prevention: Staying Off Blacklists

Monitor proactively, not reactively. Run a blacklist check monthly, not just when something goes wrong. Catching a listing early prevents it from impacting a large campaign.

Use a reputable email service provider. ESPs manage IP reputation, handle bounce processing, and maintain feedback loop registrations. Their infrastructure is tuned to stay off blacklists.

Keep complaint rates below 0.1%. Gmail's Postmaster Tools and other feedback loop programs report complaint rates. Above 0.1% is concerning; above 0.3% typically results in deliverability problems.

Process unsubscribes and bounces immediately. Continuing to send to addresses that have bounced or unsubscribed is a quick path to blacklisting.

Authenticate properly. SPF, DKIM, and DMARC don't prevent blacklisting but are prerequisites for good reputation — unauthenticated email is more likely to be treated as suspicious.

Frequently Asked Questions

How do I find my outgoing mail server IP? Send an email to your own address, open the message, and view the full headers. The topmost Received: line (or the line containing by [mail server]) will show the IP. Your ESP should also display sending IPs in their dashboard.

Is being on the PBL (Spamhaus Policy Block List) serious? PBL listings are policy-based, not spam-based. They apply to dynamic IP ranges by design and can be removed if your ISP registers your static IP as a legitimate mail server. For most businesses, the right fix is to use a dedicated email sending service rather than sending directly from a dynamic IP.

Can a blacklist listing affect inbound email too? Primarily it affects outbound deliverability (your emails to others). In rare cases, some inbound spam filters also check the sending IP of inbound connections against blacklists — but your domain's blacklist status primarily matters for outbound.

How quickly do deliverability problems appear after being listed? Almost immediately for active sending. Mail servers query DNSBLs in real time during delivery. A listing can start causing rejections within minutes of being added.

Is the blacklist checker free? Yes — completely free, no sign-up needed.

Spam blacklist listings are silent deliverability killers — emails bounce or go undelivered without obvious error messages to the sender. A regular blacklist check takes 30 seconds and catches problems before they affect your audience at scale.

Try the Blacklist Checker free at sadiqbd.com — check your IP or domain against all major spam blacklists instantly.