Understanding UCEPROTECT blocklist listings
Overview
Section titled “Overview”Some email recipients or monitoring tools may report that IP addresses associated with Opensense are listed on the UCEPROTECT blocklist. This article explains what UCEPROTECT is, its relevance to email deliverability, and how Opensense handles such listings.
What is UCEPROTECT?
Section titled “What is UCEPROTECT?”UCEPROTECT is an independent blocklist that aggregates IP addresses based on its own unpublished criteria. It often lists broad IP ranges, including ranges used by major cloud providers and reputable email service platforms.
Its key characteristics:
- UCEPROTECT doesn’t offer transparent or auditable listing criteria.
- Its blocklist includes entire network ranges, which may include legitimate, high-volume email senders.
- Delisting is only available through a paid “express” service, which isn’t consistent with industry standards for responsible blocklist operation.
Industry best practices
Section titled “Industry best practices”According to industry-recognized guidelines in RFC 6471, blocklists that charge for delisting, or lack transparency, aren’t considered reliable indicators of email reputation. Specifically, the standard states:
“The practice of requiring a listee to pay for delisting from a negative-connotation DNSBL steers perilously close to notions of extortion… Even when such accusations are entirely unjustified, the practice causes uproar and damage to the DNSBL’s reputation.”
Based on this, and on similar evaluations by deliverability professionals across the email industry, UCEPROTECT isn’t widely trusted or used by leading mailbox providers.
Impact on deliverability
Section titled “Impact on deliverability”Opensense has done extensive monitoring and analysis of the deliverability impact of UCEPROTECT listings. Key findings:
- Major inbox providers, such as Gmail, Outlook, and Yahoo, don’t reference UCEPROTECT in their spam filtering systems.
- Less than 0.001% of Opensense email volume is routed to recipients that rely on UCEPROTECT as part of their filtering stack.
- No measurable or legitimate deliverability failures have been linked to UCEPROTECT listings.
Opensense policy
Section titled “Opensense policy”Opensense continuously monitors deliverability performance across our network. Based on all the available data:
- We don’t escalate or intervene in UCEPROTECT listings, because they don’t reflect actual risk or impact.
- Listings of this kind are expected, and commonly affect email platforms that send on behalf of many customers.
- Our team prioritizes deliverability signals that are credible, traceable, and aligned with real-world delivery behavior.
When to contact support
Section titled “When to contact support”If you believe a specific email failed to deliver because of a UCEPROTECT listing, contact our support team at help@opensense.com, and include:
- The full message headers and delivery logs
- Any bounce or rejection notices you received
- The recipient domain where the issue occurred
Our team will investigate the issue in detail, and give guidance based on verified deliverability data.