How to Check If Your Domain or IP Is Blacklisted

If your email is bouncing or landing in spam, one of the first things to rule out is a blocklist entry. Learning how to check if your domain is blacklisted takes two separate lookups: one for the IP address your mail is sent from, and one for the domain in your From address. They live on different lists and fail in different ways, so you check them one at a time.

The hard part is not running the check — it is reading the result. A tool that shouts "you are on 4 blacklists!" is often counting lists no mail server has enforced in years. This guide shows you how to query the lists that matter directly, and how to tell a real problem from noise.

The short answer#

Check the sending IP and the domain as two separate objects. The fastest route is Spamhaus's own reputation checker at check.spamhaus.org: enter an IP address or a domain, and it reports whether that object appears on a Spamhaus list.

If you want the raw answer with nothing interpreting it for you, run a DNS query yourself. An IP is queried against the zen.spamhaus.org zone; a domain is queried against dbl.spamhaus.org. A reply in the 127.0.0.x range (for an IP) or 127.0.1.x range (for a domain) means listed. An empty reply — NXDOMAIN, "no such domain" — means not listed.

Being listed is not the same as being blocked. Gmail and Outlook.com weigh their own reputation data far more heavily than any public list, so treat a listing as a lead to investigate, not a verdict.

Before you start: find your real sending IP and domain#

You cannot check the right IP until you know which one your mail actually leaves from. If you send through Google Workspace, Microsoft 365, or an email service provider, the sending IP is theirs — usually shared with thousands of other senders — not a machine you control.

To find the IP a message was sent from, open a message you sent, view its full headers, and read the earliest Received line. That is the IP that reached the recipient's server. Your domain is simply the part after the @ in your From address.

• Shared IP (Gmail, Microsoft 365, most ESPs): a listing is usually the provider's problem to manage, not yours.
• Dedicated IP (your own mail server, or a dedicated ESP plan): a listing is yours, and delisting is your job.
• Your domain: checked against domain lists such as Spamhaus DBL, independent of whichever IP sent the mail.

How to check, step by step#

Do the web check first for a quick read, then confirm with a direct DNS query when you want to see the exact list and the reason behind a listing.

1. 1

   Run the sending IP through Spamhaus

   Go to check.spamhaus.org, enter the IP from your headers, and submit. The checker reports whether it sits on the SBL, CSS, XBL, or PBL — the four IP lists bundled into Zen.

2. 2

   Run the domain through the same checker

   Enter your domain next. This checks it against the Domain Blocklist (DBL), which lists domain names — never IP addresses — seen in spam, phishing, and malware.

3. 3

   Confirm with a direct DNS query (optional)

   For an IP, reverse the four octets and append the zone. To check 192.0.2.10, query 10.2.0.192.zen.spamhaus.org. For a domain, append the zone to the name, for example example.com.dbl.spamhaus.org.

4. 4

   Read the answer

   Any A record in the 127.0.0.x range (IP) or 127.0.1.x range (domain) means listed, and the last octet tells you which list and why. An empty result or NXDOMAIN means not listed.

5. 5

   Cross-check the provider's own reputation

   Because the big receivers score you separately, open Google Postmaster Tools and Microsoft SNDS for your sending domain. A poor reputation there affects inbox placement more than most public listings do.

Reading the return codes#

A DNSBL answers with a fake IP address that acts as a code, not a real destination. The zone you queried and the last octet together tell you which dataset flagged the object and what it was flagged for.

For an IP, the four Zen datasets each carry their own return code:

For a domain, the DBL uses the 127.0.1.x range, with the last octet naming the reason:

Which blocklists actually matter#

Most "you're on N blacklists" tools query dozens of lists at once, then colour the results red without telling you which lists a real mail server ever consults. A handful carry almost all the weight; the rest are informational, private, or defunct.

Is the listing worth acting on?#

Before you spend an afternoon on a delisting request, decide whether the listing can actually hurt you. Two questions settle most cases: does a list that real receivers enforce show your object, and does your reputation at Gmail or Outlook.com look bad at the same time?

If a major list is clean and your provider dashboards are healthy, a red mark on an obscure aggregator is noise. If Spamhaus or a provider dashboard agrees something is wrong, that is a real signal worth chasing.

The netblock row is where readers panic without cause. Some lists deliberately flag entire IP ranges or whole networks, so a single shared address can appear listed because of a neighbour's behaviour rather than yours — and the big mailbox providers largely ignore those lists for exactly that reason.

What to do when the check looks wrong#

Two false alarms account for most of the confusion, and both come from how the query was run rather than from a real listing.

The second trap is reading NXDOMAIN as a failure. In DNSBL terms, "no such domain" is the good answer — it means the object is not on the list. An empty result is a clean result, not a broken query.

• Listed on a real list: fix the cause first (a compromised account, poor list hygiene, or bulk sending), then request delisting. A domain relisted minutes later still has its cause in place.
• Listed only on aggregators: usually safe to ignore; recheck against Spamhaus and your provider dashboards to confirm.
• Clean everywhere but still filtered: the problem is authentication or reputation, not a blocklist — check SPF, DKIM, DMARC, and your complaint rate.

A faster way — and where it stops#

Checking by hand is a snapshot. If you send in any volume, you want a standing alarm, not a monthly lookup. The tools built for that are the mailbox providers' own — Google Postmaster Tools and Microsoft SNDS report your sending reputation and complaint rate straight from the source — plus Spamhaus's checker, which surfaces a fresh listing the moment it appears. Most email service providers show the same signals inside their dashboards.

AI Emaily is not one of those tools, and pretending otherwise would be dishonest: it is an AI email client for the mail you receive, not a blocklist monitor or a deliverability tester. Where it touches this problem is narrow — every send is approval-first, it never blasts bulk mail from your domain, and it does not train on your mail, so the client itself will not be what lands you on a list. To watch your outbound reputation, use the provider tools above. We build AI Emaily.