Last updated: July 2026

In short: The Spam and Open Relay Blocking System (SORBS) shut down permanently in 2024. Its DNS zones (dnsbl.sorbs.net) no longer answer. Mail server administrators must remove SORBS from all anti-spam checks immediately to prevent connection latency and DNS lookup timeouts.

For over two decades, the Spam and Open Relay Blocking System (SORBS) operated as one of the most widely deployed and controversial DNS-based blocklists (DNSBLs) in email administration. However, in 2024, the project was permanently discontinued.

If your mail transport agents (MTAs), legacy tutorials, or existing Postfix configurations still reference dnsbl.sorbs.net or spam.dnsbl.sorbs.net, immediate cleanup is required. Because the underlying service has ceased operations, querying those zones produces no results.

Mechanical Evidence of the Shutdown

The complete discontinuation of SORBS is mechanically verified through direct DNS queries (dig snapshots). The authoritative name servers for the domain have been decommissioned:

Querying the name servers of the primary domain returns no records: # dig +short NS sorbs.net

The exact mechanical output of this lookup is: (no answer)

Similarly, querying the canonical test entry against the SORBS DNSBL zone confirms the service is entirely dead: # dig +short A 2.0.0.127.dnsbl.sorbs.net This query also returns no DNS answer.

Why Legacy SORBS Configurations Harm Your Mail Server

If your email server (such as Postfix, Exim, Mailcow, or Microsoft Exchange) remains configured to query dnsbl.sorbs.net during inbound SMTP sessions, your infrastructure incurs noticeable operational penalties:

  1. Unnecessary DNS Latency: For every incoming connection, your server attempts to resolve the client IP against the dead SORBS zone. Because the name servers no longer exist, the query waits until your local DNS resolver reaches its timeout threshold, delaying legitimate inbound email acceptance by several seconds.
  2. Risk of Future False Positives: If the domain sorbs.net is ever re-registered by third parties or pointed to a wildcard IP address in the future, your mail server could instantly begin rejecting all inbound email traffic worldwide (all-block).

How to Remove SORBS from Your MTA Configuration

To eliminate latency and secure your inbound pipeline, audit your mail server and anti-spam configuration files immediately to purge all references to sorbs.net:

  • In Postfix (/etc/postfix/main.cf): Remove reject_rbl_client dnsbl.sorbs.net and reject_rbl_client spam.dnsbl.sorbs.net from your smtpd_recipient_restrictions or smtpd_client_restrictions blocks.
  • In SpamAssassin / Rspamd: Disable legacy plugins or scoring rules that assign weights to SORBS DNSBL lookups.

Honest Verdict: Should You Care?

  • If you are a sender: NO. You cannot be listed on SORBS because the database no longer exists. If a third-party reputation monitoring tool claims your IP address is listed on SORBS, that tool is displaying outdated, cached data.
  • If you are a mail server administrator: YES — clean up immediately! Check your active MTA configurations and remove SORBS from your real-time blocklist checks right away to ensure fast, unhindered inbound mail delivery.

Verifying your configuration

To ensure that your mail server configuration is fully optimized after removing deprecated blocklists and adheres to modern authentication protocols (SPF, DKIM, and DMARC), audit your domain instantly using the free MXAudit scanner.

Further reading

  • DNS verification dig +short NS sorbs.net (retrieved: July 17, 2026)
  • DNS verification dig +short A 2.0.0.127.dnsbl.sorbs.net (retrieved: July 17, 2026)