What it is
UCEPROTECT operates three DNSBL levels with progressively broader scope. Level 1 lists individual IPs that have sent spam. Level 2 escalates to list entire IP ranges within an ASN if enough IPs in that range are on Level 1. Level 3 lists entire ASNs (internet service providers or hosting companies) if their aggregate spam ratio is too high. Level 2 and 3 listings can affect all senders on a shared hosting platform regardless of individual behaviour.
Ownership history
How it affects SMTP delivery
Receiving MTAs that query UCEPROTECT return 550 rejections. Level 2 and 3 listings are controversial because they block entire IP ranges and ASNs, affecting innocent senders sharing infrastructure with bad actors. Many large mail providers have removed UCEPROTECT from their filter chains because of this.
What causes a listing
Level 1: your IP sent spam that UCEPROTECT's traps detected. Level 2: too many IPs in your ASN's range are on Level 1. Level 3: your ASN has a spam-to-clean ratio exceeding UCEPROTECT's threshold.
How to get removed
Level 1 listings expire automatically after 7 days with no new spam activity. Express removal (24-hour) is available via a paid service at www.uceprotect.net. Level 2 and 3 listings can only be addressed by the ASN operator (your hosting provider), not by individual senders.
For the full reference catalog, see the email blocklist directory.
Delisting process in detail
UCEPROTECT operates three levels: Level 1 lists individual IPs, Level 2 lists /24 subnets when they contain listed IPs, and Level 3 lists entire ASNs when they harbor multiple listings. Level 1 removal is free through uceprotect.net’s lookup form, though it typically requires waiting for the automatic decay period (7 days without new spam). Level 2 and Level 3 removals are aggressive against ISPs and hosting providers: UCEPROTECT offers paid express delisting for these levels, which has drawn criticism from the mail community as coercive. Most receivers do not query Level 3 due to its extreme scope; Level 1 is the practical concern for individual senders.
Prevention practices
UCEPROTECT prevention is primarily about avoiding shared infrastructure with abusive senders. Dedicated IPs on reputable ESPs (SendGrid, Postmark, Amazon SES) are less likely to trigger Level 1 than shared IPs on budget hosting, and Level 2 and Level 3 exposure is minimized by choosing providers with clean /24 subnets and clean ASN reputation. Query dnsbl-1.uceprotect.net for your sending IP regularly. If Level 2 or Level 3 listings affect delivery, the mitigation is switching to a provider with better neighborhood reputation rather than trying to remediate the listing directly.
Common listing causes
Level 1 listings usually result from actual spam sending, either from the listed IP directly or from a shared hosting account on that IP. Level 2 (subnet) listings occur when 5+ Level 1 listings appear in the same /24; this is common on budget shared hosting with lax abuse policies. Level 3 (ASN) listings target entire hosting providers with systemic abuse problems. Some major hosting providers appear on Level 3 continuously due to the difficulty of policing thousands of customer accounts, which is why Level 3 is not widely honored by receivers.
Related blocklists
UCEPROTECT is one of several subnet-aggregating blocklists; NIX Spam and IX Manitu (part of the eco Alliance) apply similar logic in the German-speaking mail community. Enterprise deployments rarely query UCEPROTECT Level 3 due to its broad scope, but Level 1 is used by some European mail providers and small ISPs. UCEPROTECT’s controversial pay-for-delisting model has led most major receivers to weight its signals lightly compared to Spamhaus or SpamCop. However, for senders reaching European recipients, monitoring UCEPROTECT is worthwhile because some receivers do act on Level 1 listings.
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
About SMTPedia
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