// Tool
DNSBL / RBL Checker
Check an IPv4 address against common DNS-based block lists. Each query reverses the IP and looks up {rev}.{rbl-zone} via DoH — an answer means the IP is listed.
IPv4 only. Uses Cloudflare DoH for queries.
Frequently Asked Questions
What is a DNSBL (DNS block list)?
A DNSBL, or RBL, is a list of IPs known for spam or abuse, published over DNS so mail servers can quickly check a sender’s reputation during the SMTP conversation.
My mail server’s IP is listed — what do I do?
Find the cause (compromised account, open relay, shared-IP history), fix it, then use the specific blocklist’s delisting process. Delisting before fixing usually leads to relisting.
Does being on one list mean my mail is rejected?
Not necessarily — each receiver chooses which lists to use and how to weight them. Being on a major, widely used list has far more impact than an obscure one.
