What is SORBS and how do I get delisted?

SORBS (Spam and Open Relay Blocking System) is a free DNS-based blocklist that targets servers sending spam, phishing, and malicious email. With around 12 million listed hosts, it's one of the larger blocklists, though its real-world impact is lower than Spamhaus because fewer major providers rely on it for blocking decisions.

Impact Level: Low-Medium. SORBS doesn't typically block email delivery directly at major mailbox providers. It primarily adds reputation signals that contribute to spam scoring rather than causing outright rejection.

SORBS zones (17 different lists):

• dnsbl.sorbs.net - Aggregate zone containing all sub-zones
• http/socks/misc.dnsbl.sorbs.net - Open proxy servers
• smtp.dnsbl.sorbs.net - Open SMTP relay servers
• web.dnsbl.sorbs.net - Compromised web servers with exploited mail scripts
• spam.dnsbl.sorbs.net - Hosts sending spam (subdivided by recency)
• escalations.dnsbl.sorbs.net - ISP netblocks tolerant of spammers
• zombie.dnsbl.sorbs.net - Compromised machines
• dul.dnsbl.sorbs.net - Dynamic IP ranges (like Spamhaus PBL)

What triggers listing:

• Sending spam to SORBS trap addresses
• Operating an open relay or proxy
• Compromised server or web application
• Using dynamic/residential IP for direct mail sending

How to check: Visit sorbs.net/lookup.shtml

Delisting process:

• Most zones: Automatic delisting once the issue is resolved (open relay closed, spam stopped)
• dul.dnsbl.sorbs.net: Requires manual request - create SORBS account and contact support
• zombie.dnsbl.sorbs.net: Also requires manual intervention
• http, socks, smtp zones: Semi-automatic after verification the issue is fixed

To request removal:

1. Visit sorbs.net/overview.shtml
2. Create an account if requesting manual removal
3. Submit removal request with explanation of the fix

SORBS is like a background check that notes every past incident. It won't lock you out of major ports, but it does add marks to your record that other systems might factor into their decisions.