Is this IP on a blocklist? Run a DNSBL reputation check
Updated:
An IP blacklist check tells you whether an IPv4 address is listed in public DNS-based blocklists (DNSBLs) that spam filters and abuse systems consult. Type any public IPv4 into the box above and the tool asks 8 anti-spam and open-proxy lists at once. Do it before you put a proxy IP behind an ad account, a store login or an email workflow, because a listing can follow that address into every service that checks it.
The eight lists this check queries
The lists fall into a few families. Spam and botnet lists record addresses that sent junk or abuse; open-proxy lists record addresses that relay traffic for anyone without a login. A hit on either family tends to lower how much a login page, payment form or mail server trusts the address.
| Zone | What it tracks | Typical effect of a listing |
|---|---|---|
bl.spamcop.net, b.barracudacentral.org | Spam and botnet activity | More CAPTCHA challenges such as Cloudflare Turnstile or hCaptcha; outgoing mail rejected |
http.dnsbl.sorbs.net, socks.dnsbl.sorbs.net | Known open HTTP and SOCKS proxies | The address is treated as a public proxy on store and social sign-in pages |
dnsbl.sorbs.net, psbl.surriel.com | Combined abuse data and compromised hosts | Lower trust with payment gateways and ad networks |
dnsbl-1.uceprotect.net, all.s5h.net | Abuse from single IPs, brute force and scraping | Automated API calls and new sign-ups get blocked |
Reading the report
- Every row CLEAN. The report confirms the IP is clean across all 8 zones. That is what you want before attaching the address to anything valuable.
- One or more rows LISTED. The row shows which list returned a match. Even a single listing is a reason not to log in to a seller or ad account from that IP.
- A listing on a SORBS proxy zone. Scanners found the address relaying traffic without a password. Public proxies end up here routinely.
- Clean, but you still see challenges. A blocklist is only one signal. Look at what kind of network the IP belongs to with the IP lookup tool.
Why shared and public proxies get listed
When many unrelated people send traffic from one public proxy, it takes only one of them running spam or credential stuffing for the address to land on SpamCop or SORBS. Separately, security crawlers scan the IPv4 space for open proxies, and any proxy that accepts traffic without authentication gets recorded in http.dnsbl.sorbs.net. That is the typical fate of addresses on a free proxy list.
ProxyV4 private IPv4 and static ISP proxies require user:pass authentication and are assigned to one customer for the whole rental, so no stranger is sending traffic from your address.
Step by step
- 1
Get the exit IP
Use the IPv4 your proxy exits from. If you are unsure which one that is, the proxy checker reports it.
- 2
Run the check
Paste the address and start the check. The server reverses the octets (
d.c.b.a.zone) and asks all 8 zones in parallel. - 3
Read every row
Each zone is marked CLEAN or LISTED. A fully clean result is confirmed at the top of the DNSBL Reputation Report.
- 4
Retire listed addresses
Do not use an IP that appears on even one list for accounts you cannot afford to lose; switch to another address.
Frequently asked questions
How does a DNSBL lookup work?
To test 1.2.3.4 against bl.spamcop.net, a resolver asks for the A record of 4.3.2.1.bl.spamcop.net. An NXDOMAIN answer means the IP is not listed; an answer in the 127.0.0.x range means it is.
A free proxy I found showed LISTED on SORBS. Why?
Public proxies accept traffic without authentication, so scanners find them and add them to the SORBS open-proxy zones (http.dnsbl.sorbs.net and socks.dnsbl.sorbs.net). For account work, use private proxies that require a login.
Should I also check the ASN?
Yes. Once an IP comes back clean, run it through the IP lookup tool to see whether its ASN belongs to a residential ISP or a hosting provider.
Does this check IPv6 addresses?
No. It takes a public IPv4 address.
An address no stranger has used alongside you
ProxyV4 private IPv4 and static ISP proxies sit behind username and password login and go to one customer per IP.
See static ISP prices