Last updated: July 2026

In short: UCEPROTECT classifies listings across three distinct levels: Level 1 flags individual IP addresses for direct abuse, while Level 2 and Level 3 block entire subnets or Autonomous Systems. Because of its controversial paid whitelisting scheme (whitelisted.org) and admitted collateral damage, Level 2 and Level 3 listings are ignored by major email providers and should never be paid for.

Encountering rejection logs referencing dnsbl-1.uceprotect.net, dnsbl-2.uceprotect.net, or dnsbl-3.uceprotect.net frequently alarms mail server administrators. UCEPROTECT operates as one of the most controversial DNS-based blocklists (DNSBLs) in the industry. To evaluate its impact correctly, administrators must distinguish between its three escalation tiers.

The 3 Levels of UCEPROTECT Explained

Level 1 — Individual IP Address Listing

Level 1 targets the specific, single IP address directly responsible for transmitting bad traffic or abuse. In official documentation, the exact triggers are defined: IP's get listed in Level 1 automatically if they either try to deliver e-mails to spamtraps or if they try to break an SPF Record by forwarding mail that is forbidden by the SPF-Record or if they falsify senders with SRS while no SPF is set for the sender domain or if they are involved in port scans or probes or any kind of attacks against our servers.

Level 2 — Subnet Escalation

When multiple IP addresses within a shared netblock trigger Level 1 alerts, UCEPROTECT escalates the block to neighboring IP allocations: Level 2 escalates within allocation

Level 3 — Autonomous System (ASN) Blocks

Level 3 penalizes the entire Autonomous System (ASN) of a hosting or cloud provider—often listing hundreds of thousands of unrelated IP addresses across platforms like Hetzner, OVHcloud, DigitalOcean, or Linode. UCEPROTECT explicitly acknowledges the indiscriminate nature of this tier: Level 3 lists IP Space of the worst ASN's. This blacklist has been created for HARDLINERS. It can, and probably will cause collateral damage to innocent users when used to block email.

Checking Status and the Paid Whitelisting Scheme (whitelisted.org)

You can check whether your IP address appears on any UCEPROTECT zone for free at www.uceprotect.net. However, resolution workflows differ drastically depending on the listing level:

  • For Level 1: Once the underlying vulnerability or forwarding loop is corrected, the single IP expires automatically after 7 consecutive days of clean traffic. A paid express removal option is also offered by the operator.
  • For Level 2 and Level 3: Because these tiers flag entire subnets and data center networks based on the behavior of other customers on the same host, individual administrators cannot technically fix the root cause. At this stage, UCEPROTECT directs users to its commercial exclusion platform, whitelisted.org: This means if your Netrange or Provider gets listed in UCEPROTECT Level 2 or 3, then your IP will by excluded and marked as clean, if registered with us. This is done as long as your subscription is valid and your system is NOT listed in UCEPROTECT Level 1 for abuse.

Under this model, administrators are asked to pay ongoing subscription fees to exempt their clean IP addresses from blanket Level 2 and Level 3 network blocks caused by unrelated third parties.

Honest Verdict: Should You Care?

  • For Level 1: YES. A Level 1 listing indicates genuine technical misconfigurations or security compromises originating from your server (such as hitting honeypots, breaking SPF during forwarding without SRS, or port scanning). Fix the underlying issue and wait out the 7-day expiration period.
  • For Level 2 & Level 3: NO — never pay! You should completely ignore Level 2 and Level 3 listings. Reputable, Tier-1 email providers—including Google Workspace, Microsoft 365, Apple iCloud, and Yahoo—do not use UCEPROTECT Level 2 or Level 3 in their filtering firewalls because of its intentional collateral damage (can, and probably will cause collateral damage to innocent users) and subscription practices. If a smaller receiving server bounces your email due to Level 2 or Level 3, the misconfiguration lies in their overzealous adoption of an unreliable blocklist. Never pay exclusion fees on whitelisted.org.

Verifying your configuration

To verify that your mail server properly handles email forwarding without breaking SPF records and publishes valid DKIM and DMARC authentication policies, audit your domain instantly using the free MXAudit scanner.

Further reading