Spam and Open Relay Blocking System (SORBS) DNSBL blacklist


The Spam and Open Relay Blocking System (SORBS) DNSBL blacklist is a Domain Name System-based Block List (DNSBL). This blacklist is SORBS’ aggregate blacklist that blocks email from host servers known to distribute spam, phishing attacks, and other forms of malicious email.

  • Listings occur at the IP and domain level.
  • The impact on deliverability is low.

Reasons for getting listed

IP addresses are listed for:

  • Sending email that fails to follow best practices from the CAN-SPAM act
  • Sending spam from compromised accounts, or spam that is generated by viruses, malware, trojan or botnet infections in a network
  • Having servers that have trojan infestations, dynamically allocated IP addresses, or have been hacked and hijacked
  • IP addresses and networks that have requested omission from SORBS scanning and processing
  • Open relays

How to get off this blacklist

This blacklist automatically removes IP addresses or domains after the issue is fixed from the last receipt of spam to its spam traps.

This blacklist also accepts manual requests to remove IP addresses. First you need to register for an account with SORBS. Then you can look up IP addresses and netblocks in the SORBS database and open support tickets.

If you are eligible, you can manage your own networks and listings, and even remove your own IP addresses.

Tips for staying off this list

  • Maintain strict security on your sending IP addresses
  • Monitor your mail for unknown campaigns
  • Monitor feedback loops for complaint increases
  • Make sure your servers are properly configured and have no open relays
  • Audit your email program to make sure you are CAN-SPAM compliant
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