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Glossary Networking

DNSBL (DNS blocklist)

A DNSBL is a DNS-based list of IP addresses known for sending spam or abuse, which mail servers query to decide whether to accept a message.

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In more detail

To check 192.0.2.1 a server queries 1.2.0.192. followed by the list's domain, reversing the octets. An answer in 127.0.0.0/8 means the address is listed; no answer means it is not. Being listed explains why legitimate mail sometimes bounces.

Try these tools

DNSBL Blacklist Checker

Check whether an IPv4 address is listed on major public DNSBL/RBL spam blocklists (Spamhaus, SpamCop, Barracuda).

See also

  • Glossary IP address
    An IP address is the number that identifies a device on a network so that data can be sent to it.
  • Glossary SPF
    SPF (Sender Policy Framework) is a DNS record listing which servers may send email for a domain.
  • Glossary Domain name
    A domain name is the human-readable address of a website or service, such as example.com, which DNS translates into an IP address.
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