https://www.spamhaus.org/blocklists/policy-blocklist/
Policy Blocklist (PBL) | DNSBL for effective email filtering
A dataset containing end-user IP address ranges from which email should never be sent directly to the final destination.
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https://www.spamhaus.org/blocklists/domain-blocklist/
Domain Blocklist (DBL) | Domain DNSBL for email filtering
The Domain Blocklist contains domains showing signs of spam or malicious activity, including those owned by bad actors, or hijacked legitimate domains.
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https://www.spamexperts.com/
Email filtering and archiving solutions - SpamExperts
Mar 26, 2026 - N-able SpamExperts offers professional anti-spam email filtering and archiving for Web hosting providers, Internet Service Providers and Telcos.
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https://datatracker.ietf.org/doc/html/rfc5435
RFC 5435 - Sieve Email Filtering: Extension for Notifications
Sieve Email Filtering: Extension for Notifications (RFC 5435, )
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https://www.spamhaus.org/blocklists/exploits-blocklist/
Exploits Blocklist (XBL) | IP DNSBL for email filtering
The Exploits Blocklist flags compromised IPv4/IPv6 addresses that have been hijacked to use by third-party exploits.
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https://www.spamhaus.org/blocklists/combined-spam-sources/
Combined Spam Sources (CSS) | IP DNSBL for email filtering
An SMTP traffic blocklist, listing port-25 based detections due to unsolicited emails, poor list hygiene, or compromised accounts sending malicious emails.
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https://www.spamhaus.org/blocklists/
Blocklists | Trusted, actionable DNSBLs for email filtering
Spamhaus DNS Blocklists (DNSBLs) help email administrators filter emails and protect users from phishing, malware, spam and more.
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https://www.spamhaus.org/blocklists/spamhaus-blocklist/
Spamhaus Blocklist (SBL) | IP DNSBL for effective email filtering
Spamhaus Blocklist contains IPs identified as sending spam, hosting malicious content, hijacking IP space, or acting like a bulletproof hosting company.
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https://www.spamhaus.org/blocklists/zen-blocklist/
ZEN Blocklist | Combined IP DNSBLs for effective email filtering
The Zen blocklist contains all IP-based DNSBLs offered free by Spamhaus (SBL, CSS, XBL, and PBL) to make querying simpler and faster.
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https://www.duocircle.com/content/email-filtering-service
What Do You Need To Know About Email Filtering Services? - DuoCircle
What is email filtering services, why you need them, and how you should approach making the right choice for yourself.
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https://mxguarddog.com/
Anti-Spam Filtering Service - Email Security By MXGuarddog
Cloud hosted anti-spam and antivirus protection for domain owners, stop email born threats before they reach your network.
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https://www.duocircle.com/content/outbound-spam-filtering
Outbound Spam Filtering Has A Significant Role To Play In Reducing The Spread Of Spam Email...
Block spam attempts at the initial stage and reduce spam from flooding the internet.
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https://www.spamhaus.org/resource-hub/email-security/best-practice-dnsbls-and-email-filtering-how-to-get-it-right/
Email Security | BEST PRACTICE | DNSBLs and email filtering - how to get it right
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https://mxguarddog.fr/
Anti-Spam Filtering Service - Email Security By MXGuarddog
Cloud hosted anti-spam and antivirus protection for domain owners, stop email born threats before they reach your network.
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