What is SORBS and how do I get delisted?
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You ran a blocklist check and spotted your IP or domain sitting on SORBS. Now you're wondering how worried to be. The short answer: less worried than if you'd found yourself on Spamhaus, but it's still worth fixing.
SORBS (Spam and Open Relay Blocking System) is a free DNS-based blocklist that tracks servers known for sending spam, phishing, and malicious email. It's a big list, around 12 million listed hosts, but its real-world impact is lower than some other blocklists because fewer major mailbox providers use it as a hard blocking signal. Think of it as adding a mark to your sending reputation rather than slamming the door on delivery.
SORBS runs 17 different zones. The ones you're most likely to encounter are:
- spam.dnsbl.sorbs.net. Hosts caught sending spam (split by how recent the activity was)
- smtp.dnsbl.sorbs.net. Open SMTP relay servers
- zombie.dnsbl.sorbs.net. Compromised machines being used to send mail
- dul.dnsbl.sorbs.net. Dynamic or residential IP ranges (similar to the Spamhaus PBL)
- web.dnsbl.sorbs.net. Web servers with exploited mail scripts
- http/socks/misc.dnsbl.sorbs.net. Open proxy servers
- escalations.dnsbl.sorbs.net. ISP netblocks that tolerate spammers on their network
- dnsbl.sorbs.net. The aggregate zone that includes everything above
Common triggers for a SORBS listing include hitting spam trap addresses, running an open relay or proxy, sending from a compromised server or web application, or using a dynamic or residential IP to send mail directly.
To check if you're listed, visit SORBS directly and look up your IP or domain.
Getting delisted depends on which zone caught you.
- Most zones (spam, smtp, http, socks) delist automatically or semi-automatically once the underlying issue is resolved. Close the open relay, stop the spam, patch the compromised script, and SORBS will eventually clear the listing on its own.
- The dul zone requires a manual request. You'll need to create a SORBS account and contact their support team directly.
- The zombie zone also needs manual intervention since it flags machines that were actively hijacked.
For a manual removal request, go to sorbs.net, create an account, and submit a removal request with a clear explanation of what happened and what you've fixed. Be specific. Vague requests tend to go nowhere.
(Worth noting: if you're on SORBS and also showing up on Spamhaus or Barracuda, tackle those first. Those carry significantly more weight with major providers.)
Not sure which blocklists are actually affecting your delivery? Our free blocklist checker shows you where your domain or IP stands across the lists that matter most. And if you're dealing with something more urgent, our SOS hotline is free to use.
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