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Spamhaus Hash Blocklist

The Spamhaus Hash Blocklist (HBL) is a collection of cryptographic hashes of elements or "tokens" found in spam emails that Spamhaus believes to be malicious or suspicious. Using the HBL allows mail receivers to filter their inbound mail by comparing those tokens, via their hashes, to identical tokens in the mail they receive.

  • The HBL stores and queries its elements as a cryptographic hash, where each hash is unique to each element.
  • Elements presently listed by HBL include email addresses, file attachments, and cryptographic wallet accounts. New types of elements may be defined in the future.
  • More in-depth technical information can be found in the Spamhaus Technology Ltd documentation of the HBL.

Expiration and Removal

  • Spamhaus identifies the specific value of each defined element in spam we receive, computes the hash, and delivers that reputation data to postmasters.
  • Postmasters decide how they will use that reputation data.
  • Hashes listed in the HBL will expire over time.

If you believe that your mail is being blocked due to a hashed element published on the Spamhaus HBL, please go to the HBL Lookup form and follow the instructions.

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