Email blocklist · DNSBL · IP addresses MON · 14 SEP 2026

SORBS DNSBL

Operated by Proofpoint · Australia · Zone dnsbl.sorbs.net

About

Spam and Open-Relay Blocking System. Operated by Proofpoint after acquiring it. Multiple sub-zones available; dnsbl.sorbs.net is the aggregate. Notably stricter listing criteria than Spamhaus; some operators consider it over-broad.

Listing criteria

Composite list including spam sources, open relays, open proxies, vulnerable hosts and dynamic IP space. Several sub-zones available for granular filtering.

How to query

For an IP address 1.2.3.4, query reversed-octets-dot-zone:

dig +short 4.3.2.1.dnsbl.sorbs.net

A returned IP (such as 127.0.0.2) means listed. Each blocklist has its own set of return codes meaning different things; the operator's documentation explains theirs.

Operator site Delisting / lookup › Return codes ›