Spam and Open Relay Blocking System (SORBS) Dynamic User and Host List (DUHL) blacklist


The Spam and Open Relay Blocking System (SORBS) Dynamic User and Host List (DUHL) blacklist includes subnets that reject email from entire ranges of IP addresses. This includes hosting companies that send spam as well as single IP addresses that may fall in that range of IP addresses. This blacklist blocks email from servers known to distribute spam, phishing attacks, and other malicious forms of email from dynamically assigned IPs.

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

Reasons for getting listed

Your IP address may be listed if:

  • It was dynamically assigned at one time
  • It was a static IP address without a unique pointer (PTR) record

How to get off this blacklist

This blacklist 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 blacklist

  • Confirm that your IPs have valid PTR records in DNS that resolve to the correct hostname
  • Make sure your servers are properly configured and have no open relays or open proxies
  • Conduct ongoing security checks
  • Ensure you are not sending email over dynamically assigned IP addresses
Was this article helpful?
0 out of 0 found this helpful
Have more questions? Submit a request