How to Check if an IP Address Is Blacklisted (One IP or a List)

To check whether an IP address is blacklisted, ask each email blocklist whether it lists the address; they answer over DNS. Paste your sending IPs into the bulk IP blacklist checker and it queries Barracuda, SpamCop, PSBL and Mailspike, then shows which lists the IP is on, the reason each gives and a removal link. For one IP with a fuller breakdown, use the IP blacklist check.

Most deliverability problems that blame "a blacklist" are not a listing at all, so it is worth a two-minute check before you change anything else. This guide shows how the lookup works, how to read the answers and what to do next.

Step 1: find the IP your mail is sent from

Blocklists list the IP that connects to the receiving server, not your domain or your address. If you run your own mail server, that is its public IPv4 address. If you send through Google Workspace, Microsoft 365 or an email platform, the sending IPs belong to them, and a listing there is theirs to fix.

To find the IP from a message you sent, open the full headers in the received copy and read the Received line added by the recipient's server. The IP in brackets is the one that connected. Our guide to finding who owns the IPs in a bounce or email header walks through it.

Step 2: run the check

Paste the IPs, one per line, and press Check IP addresses. You can paste up to 25 IPv4 addresses without an account, or 100 after a free Google sign-in, counted over ten minutes. Log lines are fine: the first IP on each line is used. IPv6, private and reserved addresses are skipped.

The limit is lower than on our other bulk tools because the check queries other people's DNS servers, and we would rather stay inside their usage terms.

How the lookup works

A DNS blocklist (DNSBL) is a DNS zone, and a listed IP has a record in it. To check 203.0.113.10, you reverse the octets and ask for 10.113.0.203 followed by the list's zone name. No answer means not listed. An answer in 127.0.0.x means listed, and the last number says why. RFC 5782 describes the format.

The same RFC requires every list to carry a test entry at 127.0.0.2, so anyone can confirm the list is working. The tool asks each list for its own test entry too. That matters because a list that is rate-limiting or refusing you can look exactly like a clean answer. If a list does not return its test entry, the row says Unclear rather than Not listed.

Step 3: read each row

Result	What it means	What to do
Listed	A list holds the IP. The row names the list, the reason it gives and links to its lookup page	Find the cause, then follow that list's removal steps
Not listed	Every list answered and none holds the IP	Nothing to fix on blocklists. Look at authentication, complaints and bounces next
Unclear	At least one list did not answer in a trustworthy way. The row names it	Run the IP again later, or check that list by hand
Not checked	IPv6, private or reserved address	Use a different check for IPv6

Which lists are checked, and why not Spamhaus

The bulk run queries four IPv4 lists with free public DNS access: Barracuda (BRBL), SpamCop, PSBL and Mailspike BL. Spamhaus ZEN is left out because Spamhaus's free DNS service is for low-volume, non-commercial use, and this is a commercial site. To check an IP there, use check.spamhaus.org, which is free to use by hand. Our guide to Spamhaus listings explains what each Spamhaus return code means.

That means a clean result here is one answer from four lists, not a verdict from every list in existence. Lists differ in how they list and how long a listing lasts, and mailbox providers run private reputation systems that no public checker can see. Our post on domain, IP and mailbox reputation explains how those layers fit together.

Step 4: what to do about a listed IP

Fix the cause first, then request removal; asking before the problem stops usually gets you listed again. The usual causes are mail to addresses that do not exist, spam traps on an old or bought list, or a compromised account sending spam. SpamCop listings expire on their own about 24 hours after reports stop. Others need a request through the list's own page, which each Listed row links to.

Work through the steps in how to get off a blacklist. If the cause is bounces, the fix is on the list side: verify the addresses you send to before the next campaign.

Check many IPs in one go

Cold email teams with several servers, agencies auditing a client's tools, and hosting teams checking a block of mail IPs can paste a whole list and download one CSV row per IP. Run it before a campaign, after an abuse complaint, and when a new sending IP is assigned to you.

What this check cannot do

• It checks four public IPv4 lists. Spamhaus ZEN and the lists mailbox providers keep privately are not included.
• Not listed is a point-in-time answer. A list can add the IP minutes later.
• It cannot tell you whether Gmail or Microsoft trust the IP.
• IPv6, private and reserved addresses are skipped.
• The limit is 25 IPs per ten minutes without an account and 100 signed in.

Keep the list clean so the IP stays clean

An IP is usually listed because of what it sent to, and bounces are the most common trigger you control. Upload the list you send to on the verify page: the first 100 email checks are free with a Google sign-in, no card. Each address comes back valid, risky or invalid with a reason, and you can download only the safe-to-send rows. Nothing is sent to anyone on the list. For larger or recurring lists, see bulk email verification, list cleaning and pricing.

Check your IPs now

Paste them into the bulk IP blacklist checker, or check a single IP in full with the IP blacklist check.