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THREATINT DNSBL is a database of IP addresses from which we recommend not to accept email - IP Addresses listed are known to conduct malicious activities including but not limited to sending spam and scanning hosts. DNSBL can be queried in realtime, allowing mail server administrators to identify, tag or block incoming connections.

How to use
Data quality
Terms of use

How to use

DNSBL can be used by all modern MTAs (mail transport agents), mail servers, or proxies by configuring the anti-spam DNSBL feature to query


Depending on the vendor, anti-spam DNSBL feature may also be called DNS Black Lists, DNS-Based Blacklisting, or IP DNS Blocklist filtering Please see to your vendor documentation for details.

DNSBL is RFC#5782 compliant.

Data quality

  • Only IP addresses conducting malicious activities (including but not limited to sending spam and scanning hosts) will be added to our DNSBL.
  • Our aim is to never affect legitimate users by adding IP addresses to our DNSBL. We therefore maintain a list of well known public APIs and services that will never be added to our DNSBL. This list includes but is not limited to the following:
    • AWS (Amazon Web Services)
    • Google APIs and Services including Gmail
    • Microsoft 365
    Kindly note that this does not apply to user instances, e.g. Amazon AWS EC2 or customers' Google Cloud resources.


We use Anycast IP addresses to route requests to the server geographically closest to you to minimise latency and maximise response times. Our network consists of servers located in data centres in:

  • Australia
  • Germany
  • Hong Kong
  • India
  • Italy
  • Singapore
  • United Arab Emirates
  • United Kingdom
  • United States of America

Terms of use

DNSBL is provided by

Please read these terms ("TERMS") carefully before using the DNSBL. Using the DNSBL implies your acceptance of these TERMS. If you do not accept these TERMS, please refrain from using the DNSBL.

  • DNSBL is provided free of charge.
  • Due to the nature of electronic communication processes, THREATINT does not guarantee or warrant uninterrupted, without delay, error-free, or omission-free operations of the DNSBL. Therefore, the information contained in the DNSBL is 'as is' without warranties of any kind, expressed or implied, including accuracy, timeliness and completeness.
  • In no event shall THREATINT or any of its employees or partners be liable for any direct, indirect, incidental, special, exemplary, punitive, consequential or other damages (including but not limited to, liability for loss of use, data or profits), without regard to the form of any action, including but not limited to contract, negligence or other tortious actions, arising out of or in connection with the use of the DNSBL.

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