How important are SPAMCOP and SORBS blacklists for email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 10 Jun 2025
Updated 15 Aug 2025
7 min read
When managing email deliverability, understanding the various blacklists (or blocklists) is crucial. These lists play a significant role in determining whether your emails land in the inbox or are flagged as spam. While major blocklists like Spamhaus often get the most attention, smaller or historically prominent lists like SPAMCOP and SORBS also factor into the complex ecosystem of email filtering.
The impact of being listed on a blacklist can range from minor delivery disruptions to outright rejection of your emails by recipient mail servers. It is vital to assess the relevance and influence of each blacklist to prioritize your monitoring and mitigation efforts effectively.
Email blacklists (also known as blocklists or DNSBLs) are databases that contain IP addresses or domains identified as sources of spam or malicious email. Internet Service Providers (ISPs) and email services use these lists to filter incoming mail, protecting their users from unwanted messages. If your sending IP address or domain is listed, it signals to receiving mail servers that your emails might be unsolicited, leading to them being blocked or sent to the spam folder. You can learn more about this in our guide on an in-depth guide to email blocklists.
The efficacy and impact of these blacklists vary widely. Some are highly influential, causing widespread delivery failures, while others have a more localized or negligible effect. The ongoing evolution of spam filtering means that the importance of individual lists can change over time. Historically, blocklists had a much larger influence on deliverability, but as spam filtering has evolved, their importance has diminished in some cases. You can read more about how this has changed at Braze's article on deliverability indicators.
Many factors contribute to email deliverability, and blocklist status is just one piece of the puzzle. Sender reputation, email authentication (like SPF, DKIM, and DMARC), and engagement metrics also play crucial roles. However, a listing on a widely used blacklist can severely undermine even the best sender reputation.
The importance of SpamCop
SpamCop is one of the more recognized blacklists in the email ecosystem. It operates by collecting spam reports from its users, and if enough complaints are received against a particular IP address or domain, it gets listed. This means its listings are largely driven by direct user feedback, making it a reactive but often effective indicator of unwanted mail.
For email senders, a listing on the SpamCop Blocking List (SCBL) can lead to measurable deliverability problems, especially with smaller mailbox providers and those who heavily rely on SpamCop's data. Its real-time nature means that an IP can be listed quickly after spam complaints emerge. The good news is that SpamCop listings are typically temporary and automatically expire once the reported spam activity ceases, though manual delisting options are also available.
If you find your IP or domain on the SpamCop blacklist, it's a strong signal that you have a problem that needs immediate attention, likely related to user complaints. Ensuring your email lists are clean and sending practices are compliant helps prevent future listings. We discuss this in more detail in our article on how SpamCop listings affect email deliverability.
SpamCop impact warning
SpamCop is a high-tier blacklist that can significantly affect your email deliverability, especially to smaller internet service providers (ISPs). A listing on the SCBL indicates that your emails have generated user complaints. Act swiftly to identify the source of complaints and resolve the underlying sending issues.
Assessing the impact of SORBS
SORBS (Spam and Open Relay Blocking System) was another historically prominent email blacklist (or blocklist). For many years, it compiled lists of IP addresses and domains associated with spam, including open proxies, compromised machines, and those sending unsolicited email. Its influence was once considerable, causing email delivery issues for many organizations.
Gmail or Yahoo Mail.
A significant development that redefined SORBS's importance occurred recently. The blocklist officially shut down operations after over two decades of service. This means that as of early 2024, SORBS is no longer an active email blacklist, and its direct impact on email deliverability is now non-existent. You can confirm this by reading about SORBS's closure.
While it's always advisable to maintain a clean sending reputation, you no longer need to actively monitor or worry about listings on the SORBS blacklist. Your focus should shift to active, impactful blocklists and other critical deliverability factors.
SpamCop: current impact
SpamCop remains a relevant blacklist, especially for email senders whose traffic is frequently reported as spam by users. Its listings are based on real-time complaints, and being listed can still cause emails to be blocked or filtered, particularly by smaller mail providers that consult its list.
User-reported: Lists IPs based on direct user spam complaints.
Measurable impact: Can affect deliverability, especially to smaller ISPs.
Actionable: Indicates a need to address sending practices and list hygiene.
SORBS: historical vs. current status
SORBS was once a significant blacklist, but its influence waned over time. Crucially, as of early 2024, SORBS has ceased operations. Therefore, it no longer has any direct impact on email deliverability. This means you can remove it from your monitoring priorities.
Former influence: Historically used by some providers for spam filtering.
Diminished relevance: Its impact became minimal before its closure.
Now defunct: No longer an active threat to deliverability.
Shared IPs and managing your sender reputation
Many email senders, especially those using Email Service Providers (ESPs), send mail via shared IP addresses. A key aspect of shared IPs is that they can be listed and delisted on blacklists frequently due to the sending practices of multiple users sharing that IP. While this is a normal occurrence, it's important to monitor how long an IP remains listed and if your ESP takes action to move clients off problematic IPs. This is part of maintaining a strong overall email domain reputation.
Furthermore, if you collaborate with co-marketing partners or third parties whose emails include your domain name or link to your products, their poor sending practices can negatively impact your brand's reputation. Even if your own sending is impeccable, association with a blacklisted sender can lead to your legitimate emails being blocked or flagged as spam. Always ensure that any partners sending on your behalf adhere to strict deliverability best practices.
Factor
Description
Impact on deliverability
Shared IPs
IPs used by multiple senders. Listings can occur due to others' bad practices.
Can lead to temporary blocks; requires ESP vigilance.
Dedicated IPs
IPs used by a single sender. Reputation is solely dependent on your sending.
Full control over reputation, but misuse has direct consequences.
Co-marketing partners
Poor sending by partners can transfer negative reputation to your brand.
Risk of collateral damage to your brand's inbox placement.
Proactive strategies for email deliverability
Maintaining strong email deliverability goes beyond just reacting to blacklist (blocklist) listings. A proactive approach is essential. This involves consistent list hygiene, sending relevant content to engaged subscribers, and properly implementing email authentication protocols like SPF, DKIM, and DMARC. These measures build and protect your sender reputation, making it less likely that your emails will be marked as spam or blocked by filters, even if you encounter minor blacklist issues.
Regularly monitoring your email performance and deliverability metrics is also critical. Look for dips in open rates, increases in bounce rates, or sudden shifts in inbox placement. These can be early warning signs of underlying issues, including potential blacklist problems, before they escalate. Tools that help you check your current blocklist status are available and can be invaluable in a proactive strategy. You can also review our guide on what happens when your IP gets blocklisted.
Act quickly on SpamCop listings, as they often indicate direct user complaints and can impact smaller mailbox providers.
Prioritize monitoring blacklists with significant, measurable impacts like Spamhaus over less influential ones.
Ensure co-marketing partners adhere to strict email sending best practices to protect your brand's reputation.
Regularly clean your email lists to remove inactive or problematic addresses and minimize spam complaints.
Implement and maintain robust email authentication (SPF, DKIM, DMARC) to build and protect sender trust.
Common pitfalls
Ignoring a SpamCop listing, assuming it's minor, can lead to persistent deliverability issues with certain providers.
Over-focusing on defunct blacklists like SORBS, diverting resources from more impactful deliverability efforts.
Failing to monitor shared IP addresses, leading to unexpected blockages due to other senders' poor practices.
Not recognizing that a co-marketing partner's poor sender reputation can negatively affect your own domain's standing.
Neglecting proactive list hygiene, which is a primary cause of spam complaints and blacklist listings.
Expert tips
Understand that shared IPs on ESPs will experience frequent blacklisting; monitor the duration and ESP response.
Request redacted headers from blacklists, if available, to pinpoint the source of offending email and sender.
Continuously track your email deliverability metrics to identify underperformance before or after any blacklist listing.
Recognize that not all blacklists have the same impact; prioritize your efforts based on actual observed deliverability changes.
For transactional emails, consider providers known for excellent IP hygiene to minimize blacklist exposure.
Marketer view
Marketer from Email Geeks says they are used enough to be worried about being listed and would not ignore a listing.
2020-04-08 - Email Geeks
Marketer view
Marketer from Email Geeks says if your co-marketing partners are sending spam and their emails include your domain name or link to your products, then their poor reputation will pass to your brand at some point.
2020-04-08 - Email Geeks
Prioritizing your blacklist (blocklist) monitoring
In summary, while both SPAMCOP and SORBS were once notable in the email deliverability landscape, their current relevance differs significantly. SPAMCOP remains an important blacklist to monitor due to its direct ties to user complaints and its impact on smaller email providers. A listing here warrants prompt investigation and action to address the root cause of the complaints.
Conversely, SORBS has officially ceased operations, rendering it obsolete for current deliverability concerns. Your efforts are now better spent focusing on other active, high-impact blocklists and cultivating a robust sender reputation through consistent best practices. Effective email deliverability is a continuous process of monitoring, adapting, and optimizing your sending habits to ensure your messages consistently reach the inbox.
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
Gmail or 
Yahoo Mail.
