IP and mail server blacklist checker

Find out whether a mail server's IP address is on the spam blocklists that receivers use, with what each listing means and how to get off.

Try:

Results for github.com

Checked 2026-11-14from cache0 ms

Not listed

Not on any of the 36 lists that answered

Mailbox providers also use private reputation systems, so this is good news rather than a guarantee.

36 lists asked3 addresses

Every list

0 listed, 36 clean, 0 did not answer.

Listed

On none of the lists asked.

Did not answer

Every list answered.

Only the first 3 addresses were checked (1 more address found). Check others by entering the IP.
A clean result here does not guarantee delivery: Gmail, Outlook and Yahoo judge senders with their own reputation systems, which no public list shows.

All lists36

52.101.40.0 (mail server github-com.mail.protection.outlook.com)

List	Result	Details
Backscatterer.org	Not listed	Not listed.
Barracuda Reputation Block List	Not listed	Not listed.
blocklist.de	Not listed	Not listed.
DroneBL	Not listed	Not listed.
Mailspike BL	Not listed	Not listed.
Passive Spam Block List (PSBL)	Not listed	Not listed.
SpamCop	Not listed	Not listed.
SpamEatingMonkey SEM-BL	Not listed	Not listed.
Spamhaus ZEN	Not listed	Not listed.
UCEPROTECT Level 1	Not listed	Not listed.
UCEPROTECT Level 2	Not listed	Not listed.
UCEPROTECT Level 3	Not listed	Not listed.

52.101.60.160 (mail server github-com.mail.protection.outlook.com)

List	Result	Details
Backscatterer.org	Not listed	Not listed.
Barracuda Reputation Block List	Not listed	Not listed.
blocklist.de	Not listed	Not listed.
DroneBL	Not listed	Not listed.
Mailspike BL	Not listed	Not listed.
Passive Spam Block List (PSBL)	Not listed	Not listed.
SpamCop	Not listed	Not listed.
SpamEatingMonkey SEM-BL	Not listed	Not listed.
Spamhaus ZEN	Not listed	Not listed.
UCEPROTECT Level 1	Not listed	Not listed.
UCEPROTECT Level 2	Not listed	Not listed.
UCEPROTECT Level 3	Not listed	Not listed.

52.101.60.191 (mail server github-com.mail.protection.outlook.com)

List	Result	Details
Backscatterer.org	Not listed	Not listed.
Barracuda Reputation Block List	Not listed	Not listed.
blocklist.de	Not listed	Not listed.
DroneBL	Not listed	Not listed.
Mailspike BL	Not listed	Not listed.
Passive Spam Block List (PSBL)	Not listed	Not listed.
SpamCop	Not listed	Not listed.
SpamEatingMonkey SEM-BL	Not listed	Not listed.
Spamhaus ZEN	Not listed	Not listed.
UCEPROTECT Level 1	Not listed	Not listed.
UCEPROTECT Level 2	Not listed	Not listed.
UCEPROTECT Level 3	Not listed	Not listed.

Not checked

Our list of blocklists was last checked against live test queries on 2026-11-14. Dead lists (SORBS, CBL and others) are left out, so a list you know may be missing on purpose.

Structured result (JSON) · 14 KB

{
  "target": "github.com",
  "mode": "ip",
  "scope": "mx",
  "registryVerified": "2026-11-14",
  "notChecked": [],
  "verdict": "clean",
  "subjects": [
    {
      "kind": "ip",
      "value": "52.101.40.0",
      "source": "mx",
      "via": "github-com.mail.protection.outlook.com",
      "listed": 0,
      "clean": 12,
      "errors": 0,
      "refused": 0,
      "skipped": 0,
      "results": [
        {
          "id": "backscatterer",
          "name": "Backscatterer.org",
          "zone": "ips.backscatterer.org",
          "delistUrl": "https://www.backscatterer.org/?target=test",
          "codes": [],
          "weight": 0,
          "category": "backscatter",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 164
        },
        {
          "id": "barracuda",
          "name": "Barracuda Reputation Block List",
          "zone": "b.barracudacentral.org",
          "delistUrl": "https://www.barracudacentral.org/rbl/removal-request",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 108
        },
        {
          "id": "blocklist-de",
          "name": "blocklist.de",
          "zone": "bl.blocklist.de",
          "delistUrl": "https://www.blocklist.de/en/delist.html",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 45
        },
        {
          "id": "dronebl",
          "name": "DroneBL",
          "zone": "dnsbl.dronebl.org",
          "delistUrl": "https://dronebl.org/lookup",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 184
        },
        {
          "id": "mailspike",
          "name": "Mailspike BL",
          "zone": "bl.mailspike.net",
          "delistUrl": "https://mailspike.io/ip_verify",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 58
        },
        {
          "id": "psbl",
          "name": "Passive Spam Block List (PSBL)",
          "zone": "psbl.surriel.com",
          "delistUrl": "https://psbl.org/remove",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 121
        },
        {
          "id": "spamcop",
          "name": "SpamCop",
          "zone": "bl.spamcop.net",
          "delistUrl": "https://www.spamcop.net/bl.shtml",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 25
        },
        {
          "id": "sem-bl",
          "name": "SpamEatingMonkey SEM-BL",
          "zone": "bl.spameatingmonkey.net",
          "delistUrl": "https://spameatingmonkey.com/services",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 110
        },
        {
          "id": "spamhaus-zen",
          "name": "Spamhaus ZEN",
          "zone": "zen.spamhaus.org",
          "delistUrl": "https://check.spamhaus.org/",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 93
        },
        {
          "id": "uceprotect-1",
          "name": "UCEPROTECT Level 1",
          "zone": "dnsbl-1.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 26
        },
        {
          "id": "uceprotect-2",
          "name": "UCEPROTECT Level 2",
          "zone": "dnsbl-2.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 35
        },
        {
          "id": "uceprotect-3",
          "name": "UCEPROTECT Level 3",
          "zone": "dnsbl-3.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 26
        }
      ]
    },
    {
      "kind": "ip",
      "value": "52.101.60.160",
      "source": "mx",
      "via": "github-com.mail.protection.outlook.com",
      "listed": 0,
      "clean": 12,
      "errors": 0,
      "refused": 0,
      "skipped": 0,
      "results": [
        {
          "id": "backscatterer",
          "name": "Backscatterer.org",
          "zone": "ips.backscatterer.org",
          "delistUrl": "https://www.backscatterer.org/?target=test",
          "codes": [],
          "weight": 0,
          "category": "backscatter",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 31
        },
        {
          "id": "barracuda",
          "name": "Barracuda Reputation Block List",
          "zone": "b.barracudacentral.org",
          "delistUrl": "https://www.barracudacentral.org/rbl/removal-request",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 107
        },
        {
          "id": "blocklist-de",
          "name": "blocklist.de",
          "zone": "bl.blocklist.de",
          "delistUrl": "https://www.blocklist.de/en/delist.html",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 29
        },
        {
          "id": "dronebl",
          "name": "DroneBL",
          "zone": "dnsbl.dronebl.org",
          "delistUrl": "https://dronebl.org/lookup",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 183
        },
        {
          "id": "mailspike",
          "name": "Mailspike BL",
          "zone": "bl.mailspike.net",
          "delistUrl": "https://mailspike.io/ip_verify",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 36
        },
        {
          "id": "psbl",
          "name": "Passive Spam Block List (PSBL)",
          "zone": "psbl.surriel.com",
          "delistUrl": "https://psbl.org/remove",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 120
        },
        {
          "id": "spamcop",
          "name": "SpamCop",
          "zone": "bl.spamcop.net",
          "delistUrl": "https://www.spamcop.net/bl.shtml",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 17
        },
        {
          "id": "sem-bl",
          "name": "SpamEatingMonkey SEM-BL",
          "zone": "bl.spameatingmonkey.net",
          "delistUrl": "https://spameatingmonkey.com/services",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 111
        },
        {
          "id": "spamhaus-zen",
          "name": "Spamhaus ZEN",
          "zone": "zen.spamhaus.org",
          "delistUrl": "https://check.spamhaus.org/",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 114
        },
        {
          "id": "uceprotect-1",
          "name": "UCEPROTECT Level 1",
          "zone": "dnsbl-1.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 26
        },
        {
          "id": "uceprotect-2",
          "name": "UCEPROTECT Level 2",
          "zone": "dnsbl-2.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 26
        },
        {
          "id": "uceprotect-3",
          "name": "UCEPROTECT Level 3",
          "zone": "dnsbl-3.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 27
        }
      ]
    },
    {
      "kind": "ip",
      "value": "52.101.60.191",
      "source": "mx",
      "via": "github-com.mail.protection.outlook.com",
      "listed": 0,
      "clean": 12,
      "errors": 0,
      "refused": 0,
      "skipped": 0,
      "results": [
        {
          "id": "backscatterer",
          "name": "Backscatterer.org",
          "zone": "ips.backscatterer.org",
          "delistUrl": "https://www.backscatterer.org/?target=test",
          "codes": [],
          "weight": 0,
          "category": "backscatter",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 26
        },
        {
          "id": "barracuda",
          "name": "Barracuda Reputation Block List",
          "zone": "b.barracudacentral.org",
          "delistUrl": "https://www.barracudacentral.org/rbl/removal-request",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 107
        },
        {
          "id": "blocklist-de",
          "name": "blocklist.de",
          "zone": "bl.blocklist.de",
          "delistUrl": "https://www.blocklist.de/en/delist.html",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 29
        },
        {
          "id": "dronebl",
          "name": "DroneBL",
          "zone": "dnsbl.dronebl.org",
          "delistUrl": "https://dronebl.org/lookup",
          "codes": [],
          "weight": 0,
          "category": "exploit",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 184
        },
        {
          "id": "mailspike",
          "name": "Mailspike BL",
          "zone": "bl.mailspike.net",
          "delistUrl": "https://mailspike.io/ip_verify",
          "codes": [],
          "weight": 0,
          "category": "reputation",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 43
        },
        {
          "id": "psbl",
          "name": "Passive Spam Block List (PSBL)",
          "zone": "psbl.surriel.com",
          "delistUrl": "https://psbl.org/remove",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 120
        },
        {
          "id": "spamcop",
          "name": "SpamCop",
          "zone": "bl.spamcop.net",
          "delistUrl": "https://www.spamcop.net/bl.shtml",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 18
        },
        {
          "id": "sem-bl",
          "name": "SpamEatingMonkey SEM-BL",
          "zone": "bl.spameatingmonkey.net",
          "delistUrl": "https://spameatingmonkey.com/services",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 108
        },
        {
          "id": "spamhaus-zen",
          "name": "Spamhaus ZEN",
          "zone": "zen.spamhaus.org",
          "delistUrl": "https://check.spamhaus.org/",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 103
        },
        {
          "id": "uceprotect-1",
          "name": "UCEPROTECT Level 1",
          "zone": "dnsbl-1.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "spam-source",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 38
        },
        {
          "id": "uceprotect-2",
          "name": "UCEPROTECT Level 2",
          "zone": "dnsbl-2.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 25
        },
        {
          "id": "uceprotect-3",
          "name": "UCEPROTECT Level 3",
          "zone": "dnsbl-3.uceprotect.net",
          "delistUrl": "https://www.uceprotect.net/en/rblcheck.php",
          "codes": [],
          "weight": 0,
          "category": "collateral",
          "status": "clean",
          "meaning": "Not listed.",
          "ms": 37
        }
      ]
    }
  ],
  "summary": {
    "subjects": 3,
    "asked": 36,
    "listed": 0,
    "clean": 36,
    "errors": 0,
    "refused": 0,
    "skipped": 0,
    "weightedScore": 0
  },
  "notes": [
    "Only the first 3 addresses were checked (1 more address found). Check others by entering the IP.",
    "A clean result here does not guarantee delivery: Gmail, Outlook and Yahoo judge senders with their own reputation systems, which no public list shows."
  ],
  "dnsQueries": 38
}

What a blocklist check tells you

A DNS blocklist (DNSBL, sometimes called an RBL) is a public list of IP addresses that sent spam, were hacked, or should not send mail directly. A receiving mail server looks up the sender's address on the list in DNS, and may reject or junk the message when it finds a match.

Enter an IP address, or a domain to check its mail servers. For a domain we read its MX records and check up to three of the addresses behind them. For each address we ask a dozen live lists and show listed, not listed, or no answer for each.

Which lists we ask, and which we leave out

Many blocklist sites still query lists that closed years ago. SORBS shut down in June 2024, and the CBL was folded into Spamhaus. Asking a dead list gives nothing, or worse, an answer for everything. Each list was tried against known listed and clean addresses before we added it, and we keep only the ones that behaved. The date of that check is shown with every result.

List	What it lists	How much it matters
Spamhaus ZEN	Spam sources, hijacked ranges, infected machines and dynamic ranges	High for SBL and XBL, low for the policy list PBL
SpamCop	Addresses reported by users or caught in traps in the last day or so	Medium, and clears itself
Barracuda	Addresses Barracuda filters rate as poor reputation	Medium, important if you mail Barracuda customers
UCEPROTECT 1, 2, 3	One address, its network block, or its whole provider	Level 1 matters, levels 2 and 3 are collateral
PSBL, SEM, blocklist.de	Trap hits and reported attacks	Medium
Mailspike, DroneBL, Backscatterer	Reputation scores, infected machines, bounce abuse	Medium to low

Each list has a weight, and the summary adds up the weights of the lists you are on. A listing on the Policy Block List only says that the range is meant for end users, such as a home connection, and is not a reputation problem.

If you are listed

Find the cause firstA hacked website form, a compromised mailbox, a computer with malware, an open relay or a bulk campaign to an old list are the usual reasons. Removal requests made before the cause is fixed lead to a new listing within days.
Check your mail setupMake sure the server has reverse DNS that matches its name, and that SPF, DKIM and DMARC pass. Several lists weigh this when they decide whether to remove you.
Ask each list to delist youThe Listings tab gives a delisting link for every list. Many remove an address on their own after a few days of clean behaviour, and some charge for faster service, which you do not need.
Check again laterCome back after the list says it has removed you. Lists refresh at different speeds, and a cached answer at a receiver can last a few hours.

Domain names have blocklists as well, for the links in your mail. Use the domain blocklist check for those.

What a clean result does not cover

Gmail, Outlook and Yahoo judge senders with private reputation systems built on their own traffic. None of that appears on a public list, so a clean result here does not guarantee delivery. It tells you that the public lists that spam filters commonly use have nothing against you.

Public lists run on donated servers and ask users to keep volume low. We pace our own questions to each list and keep recent answers for a short time, so repeated checks of the same address may show the previous answer. Use the fresh option when you have just been removed.

Questions people ask

What is a DNSBL?

A DNS-based blocklist is a list of IP addresses or domains kept in DNS, so a mail server can check a sender with one fast lookup. Listings have return codes that say why, and each list has its own rules about who is added and how they are removed.

Why does the checker say a list refused us?

Some lists limit free use. Spamhaus, for one, answers with a special error code when it thinks a query is too heavy or comes from a shared resolver. We show that as a refusal, because it tells you nothing about your address. Use the list's own website for a definite answer.

Am I blocked everywhere if I am on one list?

No. Each receiver chooses which lists it uses and how much weight to give them. Being on Spamhaus SBL or XBL is serious because many large receivers use it. A listing on a small list or a policy list affects far fewer messages.

What is the difference between UCEPROTECT levels 1, 2 and 3?

Level 1 lists single addresses that sent spam to its traps. Level 2 lists whole network blocks with several bad senders, and level 3 lists all of a provider's network. Levels 2 and 3 describe your neighbours, so only the provider can clear them.

How long does it take to be removed?

It depends on the list. SpamCop and several trap-based lists expire a listing in a day or two after the spam stops. Others need a request. After removal, receivers may keep the old answer in their cache for a few hours.

Why is a shared hosting or cloud IP listed?

Other customers on the same address or network may have sent spam. Ask your provider to move you to a clean address or to clean up its range, since one customer cannot get a network-wide listing lifted.

Does this check IPv6 addresses?

Yes, but fewer lists cover IPv6. For an IPv6 address we ask only the lists that support it and mark the rest as not asked, so a short list does not look like a full clean bill.

Use it from AI, the API or the command line

Every LookupOwl tool is also a free API and an MCP tool, with no key and no account. This one is blacklist_check. Please be kind to the rate limits.

curl

curl "https://lookupowl.com/api/v1/tools/blacklist-checker?q=8.8.8.8"

MCP

claude mcp add --transport http lookupowl https://lookupowl.com/mcp

Description for AI agents · OpenAPI · llms.txt

Not on any of the 36 lists that answered

52.101.40.0 (mail server github-com.mail.protection.outlook.com)

52.101.60.160 (mail server github-com.mail.protection.outlook.com)

52.101.60.191 (mail server github-com.mail.protection.outlook.com)

What a blocklist check tells you

Which lists we ask, and which we leave out

If you are listed

What a clean result does not cover

Questions people ask

Use it from AI, the API or the command line

You might also need

DMARC checker

SPF checker

DKIM checker

Reverse DNS

DNS lookup

IP WHOIS