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Blocklists
The modern handbook on Blocklists
Track the reputation lists that can stop mail from reaching the inbox and learn how delisting works.
By
Michael Ko & Matthew Whittaker
12 featured articles
88 min read
Updated 29 Apr 2026
Spot reputation
problems before
they block the inbox.
Suped
The modern handbook on
Blocklists
Foundation
1
How email blacklists actually work: a simple guide
Learn how email blacklists and blocklists work, why listings happen, and how to check, fix, and prevent reputation issues.
9 min read
2
A guide to RBLs (real-time blackhole lists)
Learn how RBLs work, why IPs get listed, how blocklists affect delivery, and how to fix repeat listings.
10 min read
3
A guide to the different types of email blocklists
Understand the main types of email blocklists, how each blacklist affects delivery, and how to check and respond.
9 min read
Monitoring
4
What are the most important email blacklists to monitor and how do you check them?
Discover the most important email blacklists to monitor and learn how to effectively check your IP and domain status to maintain optimal email deliverability.
9 min read
5
Which email blocklists are most important for deliverability and how should they be prioritized?
Learn which email blocklists (blacklists) are most important for email deliverability, how to prioritize them, and effective strategies for monitoring and mitigation to maintain a strong sender reputation.
6 min read
6
Spam traps: what they are and how they work
Spam traps are monitored email addresses that expose poor list hygiene, risky acquisition, and sender reputation issues.
9 min read
Major blocklists
7
Spamhaus ZEN Blocklist
The Spamhaus ZEN Blocklist is a powerful and comprehensive blacklist that combines four of Spamhaus's main IP-based blocklists into a single, efficient query to enhance protection against spam and malicious email traffic.
5 min read
8
Spamhaus Domain Blocklist (DBL)
The Spamhaus Domain Blocklist (DBL) is a highly proactive domain blacklist that helps protect users by listing domains with poor reputations that are associated with spam, phishing, fraud, and malware.
4 min read
9
Barracuda Networks Barracuda Reputation Block List (BRBL)
The Barracuda Networks Barracuda Reputation Block List (BRBL) is a real-time database, a type of blacklist (or blocklist), that contains IP addresses with a 'poor' reputation for sending email, maintained by Barracuda Central's automated systems.
3 min read
Delisting and recovery
10
How can I get delisted from Spamhaus?
A comprehensive guide on how to get delisted from Spamhaus blacklists, including steps to identify the listing, remediate the root cause, and request removal for your IP or domain.
7 min read
11
What to do if your shared IP is on a Barracuda blacklist?
Discover what to do if your shared IP address ends up on a Barracuda blacklist. Learn how to identify the issue, work with your ESP, and prevent future blocklistings to ensure email deliverability.
7 min read
12
How to deal with UCEProtect listings and their aggressive practices?
Learn how to deal with UCEProtect listings and their aggressive practices. Understand the impact, delisting options, and best practices to maintain email deliverability.
8 min read
On this page
Foundation
Monitoring
Major blocklists
Delisting and recovery
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