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Spamhaus Blocklists

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    Spamhaus is an international nonprofit organization that monitors spam and cybersecurity threats. Spamhaus maintains several blocklists that providers use to stay protected from both spam and cyberattacks. These are some of their common blocklists:

    • SBL: Spamhaus Block List is a real-time database of IP addresses identified to be sources of unsolicited bulk email.
    • DBL: Domain Blocklist is a list of domain names with poor sending reputation reputation.
    • CSS: Composite Snowshoe is a component of the Spamhaus Blocklist (SBL). It primarily identifies IPs involved in snowshoeing, the act of spreading out spam over a wide range of IPs and domains.
    • PBL: Policy Blocklist is a list of IP space that should not be sending email directly to MX. These are typically IPs assigned by ISPs to broadband and dial-up customers.



    Each blocklist serves a different purpose and will have a different impact on your delivery. It is best to avoid being listed on any Spamhaus blocklist.


    Listing Reason

    Each Spamhaus blocklist focuses on a different area of spam or cybersecurity. We encourage enforcing best practices to avoid getting onto any of the Spamhaus blocklists. Implement a double opt-in policy, enforce a sunset policy, and continuously monitor your traffic.


    Mitigation Process

    Since there are several types of listings we've gone ahead and created the following articles:


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