Is UCEProtect a legitimate blacklist for email marketing and who uses it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 18 Jul 2025
Updated 15 Aug 2025
6 min read
UCEProtect is one of the more frequently discussed and often debated topics in the world of email deliverability. For senders, encountering a listing on this particular blocklist (or blacklist, if you prefer that term) can be confusing and concerning, especially if your email sending practices are otherwise legitimate. I often hear questions about its credibility and how seriously it should be taken.
The main question that arises is whether UCEProtect is a legitimate blacklist for email marketing and, if so, who actually uses it to block mail. My experience, along with widespread industry consensus, suggests that UCEProtect operates differently from traditional, widely respected blacklists.
UCEProtect is a DNS-based blacklist (DNSBL) that aims to identify and list IP addresses associated with unsolicited commercial email (UCE) or spam. It operates a tiered system, with three primary levels of blocklists: Level 1 (UCEPROTECTL1), Level 2 (UCEPROTECTL2), and Level 3 (UCEPROTECTL3). Each level expands the scope of the listing.
Level 1 lists individual IP addresses that UCEProtect's spam traps have detected sending spam. This is somewhat similar to how many other blacklists operate. However, where UCEProtect differs significantly is in its higher tiers. Level 2 targets IP subnets or ranges from service providers, and Level 3 takes this a step further, listing entire Autonomous System Numbers (ASNs) if a certain percentage of their IP space is found to be originating spam. This broad approach can lead to many innocent senders being caught in the crossfire.
The service claims to use its own spam traps and deny lists, including those from Backscatterer, to populate its database. While the concept of using spam traps is standard for blacklists, the aggressive and wide-ranging nature of UCEProtect's listings, particularly at Level 3, is what draws significant criticism and raises questions about its legitimacy for email marketing.
Level
Scope of listing
Likely impact on legitimate mail
UCEPROTECTL1
Individual IP addresses detected sending spam.
Less likely to affect innocent users, but still controversial due to listing criteria.
UCEPROTECTL2
IP subnets or ranges from service providers with spam activity.
Higher chance of legitimate senders being blocked if they share a listed subnet.
UCEPROTECTL3
Entire Autonomous System Numbers (ASNs) if a threshold of spamming IPs is met.
Very high risk of blocking legitimate emails due to extremely wide IP range listings.
Why is UCEProtect considered illegitimate?
Many email deliverability professionals and organizations widely regard UCEProtect as an illegitimate blacklist, or even an extortion racket. The primary reason for this negative perception stems from its Level 3 listings, which can blacklist vast ranges of IP addresses, including entire service providers or hosting networks, based on a few problematic IPs. This often leads to legitimate senders being blocklisted through no fault of their own, simply because they share an IP range with a bad actor.
Another significant point of contention is UCEProtect's opaque delisting process and the associated costs. Unlike most reputable blacklists that offer clear, free methods for delisting once issues are resolved, UCEProtect often charges fees for expedited removal, which is a practice widely condemned in the email industry. This business model is frequently cited as evidence of its dubious nature.
UCEProtect's approach
Broad listings: Often lists entire IP ranges or ASNs, impacting innocent senders. You can read more about the impact of UCEPROTECT Level 3 listings.
Paid delisting: Charges fees for expedited removal, a practice widely criticized as extortion.
Lack of transparency: Criteria for listing and delisting are often unclear or inconsistently applied.
Reputable blacklist's approach
Targeted listings: Primarily lists individual IPs or small subnets directly involved in spamming.
Free delisting: Provides clear, free, and automated processes for delisting once the spam issue is resolved.
Clear policies: Maintains publicly available and transparent listing and delisting policies.
Who uses UCEProtect, and what is its impact?
Despite its controversial nature, some email providers, primarily smaller or older systems, do use UCEProtect as part of their anti-spam filtering. This is often due to outdated configurations or a lack of understanding of more reputable blocklists. Historically, some German providers were noted to use at least Level 1 of UCEProtect, and some smaller Canadian ISPs, such as Sasktel, have been observed using it.
Major mailbox providers, such as Microsoft (including Outlook and Office 365) and Google (Gmail), generally do not rely on UCEProtect for their primary filtering. Their internal systems and proprietary blacklists are far more sophisticated and effective at identifying spam without the high false-positive rates associated with UCEProtect's broad listings. You can learn more about how Proofpoint affects deliverability, a common corporate filter.
The impact of a UCEProtect listing on your email deliverability for most marketing campaigns is usually minimal compared to listings on more influential blacklists. For example, being listed on SORBS or Invaluement (if still relevant for your audience) would likely have a much greater effect. However, if your audience includes recipients using one of the smaller, specific providers that do use UCEProtect, you might experience bounce backs.
For the majority of email marketers targeting mainstream ISPs, a UCEProtect listing (especially Level 3) is more of a nuisance than a critical deliverability threat. You might see occasional bounce messages referencing UCEProtect, but these are generally in low volume and indicate that the recipient's mail server is using this particular blacklist. For example, a bounce message might look like this:
Example UCEProtect bounce message
554 5.7.1 Service unavailable; Client host [XX.XX.XX.XX] blocked using rbl.hostmaster.sk; IP 1 is XX.XX.XX.XX UCEPROTECT-Level 1 listed. See http://www.uceprotect.net/rblcheck.php?ipr=
Dealing with UCEProtect listings
If you find your IP address on a UCEProtect blocklist, particularly Level 2 or 3, my advice is generally not to panic. The impact on your overall deliverability, especially to major inbox providers, is likely minimal. The most effective approach is to focus on maintaining excellent sending practices, ensuring your lists are clean, and your content is relevant and engaging. For more guidance on what to do if your IP is blocklisted, consider our article on how to deal with a UCEProtect listing.
I strongly discourage paying any fees for delisting from UCEProtect. As mentioned by TitanHQ, paying for removal only validates their questionable business model and encourages its continuation. Focus on proper sender authentication, like SPF, DKIM, and DMARC, and maintaining a clean sending reputation, which are far more critical for inbox placement.
Do not pay for UCEProtect delisting
Paying UCEProtect for delisting is strongly discouraged. It perpetuates a business model widely considered to be an extortion racket. Most major email providers do not rely on UCEProtect for their filtering decisions, making paid delisting largely ineffective for improving overall deliverability.
Views from the trenches
Best practices
Actively monitor your bounce logs to identify if UCEProtect listings are causing actual delivery failures to your audience, as this indicates specific recipients are using the blocklist.
Prioritize maintaining a pristine sender reputation by adhering to email best practices, even if UCEProtect listings seem inconsequential.
Ensure robust authentication with SPF, DKIM, and DMARC, which are critical for gaining trust with major mailbox providers.
Focus on segmenting and cleaning your email lists regularly to avoid spam traps and reduce complaint rates, regardless of UCEProtect's activity.
Educate your team on legitimate vs. illegitimate blacklists to avoid unnecessary panic or misguided efforts.
Common pitfalls
Panicking over UCEProtect listings and diverting resources from more impactful deliverability efforts, such as improving engagement.
Paying UCEProtect for delisting, which is largely ineffective and validates their controversial business model, as it provides no lasting benefit.
Ignoring legitimate bounce messages that mention UCEProtect, as this might indicate that specific, important recipients are affected by an outdated filter.
Failing to understand the difference between UCEProtect's tiered listings and how each level affects email deliverability differently.
Assuming that a UCEProtect listing means your sending practices are inherently bad, when it could simply be due to sharing an IP range with other senders.
Expert tips
UCEProtect's Level 3 blocklist is infamous for listing entire IP ranges and ASNs, which can include legitimate senders who simply share a network with spammers. Many major mailbox providers intentionally avoid using UCEProtect because of its high false-positive rate and lack of transparent delisting criteria.
While UCEProtect isn't widely used by major ISPs like Google, Microsoft (Office 365), or Yahoo, some smaller, regional ISPs or outdated corporate mail servers might still consult it. The impact is usually isolated rather than widespread.
The consensus among deliverability experts is that UCEProtect operates more like an 'extortion racket' due to its paid delisting services and aggressive, broad-brush listings. It's generally best to ignore it and focus on fundamental email hygiene and authentication.
If you experience bounces specifically mentioning UCEProtect, it indicates a particular recipient's server is using it. Rather than trying to delist, prioritize good email practices and perhaps communicate with affected recipients if they are critical.
Focus your blocklist monitoring efforts on reputable blocklists that are known to significantly impact deliverability to major providers, such as Spamhaus and Proofpoint. These lists adhere to stricter, more transparent listing criteria.
Expert view
Expert from Email Geeks says no one of significant size uses UCEProtect, especially not its Level 2 or 3 lists, although some German providers historically used Level 1.
2021-02-17 - Email Geeks
Expert view
Expert from Email Geeks notes that Level 1 lists individual IPs, while Level 3 lists entire Autonomous System Numbers (ASNs), which is the super broad list.
2021-02-17 - Email Geeks
The verdict on UCEProtect
UCEProtect is not generally considered a legitimate blacklist by most reputable email marketers and deliverability experts. Its aggressive, broad-brush listing approach, especially at Level 3, and its paid delisting services undermine its credibility as a reliable anti-spam measure. The vast majority of major internet service providers (ISPs) and mailbox providers do not use it for blocking emails.
For email marketers, encountering a UCEProtect listing is typically not a cause for alarm or immediate action beyond standard monitoring. Instead, allocate your resources and efforts towards building a strong sender reputation through consistent best practices, robust email authentication, and careful list management. This will have a far greater positive impact on your email deliverability than any concern over UCEProtect.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Major mailbox providers, such as Microsoft (including Outlook and Office 365) and 
Google (Gmail), generally do not rely on UCEProtect for their primary filtering. Their internal systems and proprietary blacklists are far more sophisticated and effective at identifying spam without the high false-positive rates associated with UCEProtect's broad listings. You can learn more about how Proofpoint affects deliverability, a common corporate filter.
