How do Spamcop blocks during an email IP warmup affect domain reputation and deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 2 Jul 2025
Updated 18 Aug 2025
8 min read
Starting the process of warming up a new IP address or domain is a critical step in establishing a positive sender reputation and ensuring your emails reach the inbox. It is a delicate balance of gradually increasing sending volume while carefully monitoring engagement and deliverability metrics. The goal is to show mailbox providers that you are a legitimate sender, building trust over time.
However, sometimes unexpected hurdles arise during this phase. One common concern I encounter is when senders experience blocks from blocklists like SpamCop, especially when they are still in the early stages of their IP warmup. This can be particularly alarming, leading to questions about whether the warmup is derailed and if it will negatively affect the hard-earned domain reputation.
Understanding what SpamCop is and how its blocks interact with your email IP warmup is vital for navigating these challenges without panicking. It is important to distinguish between various types of blocklists and their varying impacts on your sender identity, both the IP and the domain itself.
SpamCop is a real-time blocklist (RBL) that lists IP addresses reported by its users as sources of spam. It operates on a system where users submit spam, and if enough reports come from a specific IP address, that IP is listed. Mailbox providers and email servers can then subscribe to this blocklist to identify and block mail originating from these listed IPs. It is one of several widely used blocklists that email service providers may reference.
The key difference between SpamCop and some other blocklists is its reporting mechanism, which is directly tied to user submissions. This can sometimes lead to an IP being listed due to a sudden surge in spam complaints from a small number of users, rather than a broad, consistent pattern of abusive sending. However, any blocklist entry, even on a less influential one, can disrupt email flow.
When you are using a shared IP, meaning multiple senders are using the same IP address for their email campaigns, a SpamCop block (or blacklist) often stems from another user's poor sending practices. Your own careful warmup and clean list management might not prevent this, as the block applies to the entire IP. This is a common challenge with shared IPs during the warmup period, as the reputation of the shared resource can be unpredictable.
Impact on IP warmup
A SpamCop block will undoubtedly cause emails to bounce or be rejected by recipient servers that consult this specific blocklist. This means a portion of your outgoing emails may not reach their intended recipients, leading to higher bounce rates during your warmup. While this is concerning, it doesn't necessarily mean your entire IP warmup is ruined or that your domain's reputation is permanently damaged.
The primary purpose of IP warmup is to gradually build a positive sending history with Internet Service Providers (ISPs) and mailbox providers, demonstrating consistent, wanted email traffic. This process primarily focuses on how receiving servers perceive your sending patterns over time, which contributes to your sender reputation. While a SpamCop block is a negative signal, many major mailbox providers use more sophisticated, internal reputation systems that weigh various factors, not just a single public blocklist.
For the most part, a SpamCop block on a shared IP does not directly impact your domain reputation. Your domain's reputation is tied to its sending history, authentication (SPF, DKIM, DMARC), and user engagement (opens, clicks, spam complaints). If your domain's authentication is solid and your email content is good, your domain's reputation can remain strong even if the shared IP it's sending from faces a temporary blocklist entry.
Typical bounce message for SpamCop
When an email is blocked by SpamCop, the bounce message often provides clear indication. Look for specific phrases like "blocked by SpamCop" or references to spamcop.net. This helps confirm the cause of the delivery failure and allows you to address it appropriately, typically with your ESP if using a shared IP.
Example bounce messageplaintext
550 5.7.1 Service unavailable; Client host [X.X.X.X] blocked using bl.spamcop.net; Addr:X.X.X.X
http://www.spamcop.net/bl.shtml?id=X.X.X.X
Domain versus IP reputation
It is crucial to understand the difference between IP reputation and domain reputation. While they are related and both impact email deliverability, they are distinct. IP reputation is tied to the numerical address from which your emails are sent. This reputation is built (or damaged) by the sending volume, complaint rates, bounce rates, and overall sending behavior observed from that specific IP.
Domain reputation, on the other hand, is associated with your domain name (e.g., yourcompany.com). It is influenced by factors like DMARC, SPF, and DKIM authentication, the quality of your email content, how recipients engage with your emails, and direct spam complaints. Even if your IP is blocked, a strong domain reputation can help mitigate the damage, especially if the blocklist is not widely used by major ISPs.
During IP warmup, your primary goal is to establish both. When you use a shared IP, its reputation is shared among all senders. If another sender on that IP behaves poorly, it can lead to a blocklist entry that affects everyone on it, regardless of their individual sending practices. This is why a SpamCop block on a shared IP is frustrating, but it does not necessarily reflect negatively on your new domain, assuming your sending practices are impeccable.
IP reputation (shared)
Influenced by: The collective sending behavior of all users on the IP, including volume, bounces, and complaints.
Impact: Can lead to blocklist entries (like SpamCop) that affect all senders on that IP.
Mitigation: Rely on your Email Service Provider (ESP) to manage the IP's overall reputation and delisting efforts.
Domain reputation (new)
Influenced by: Your specific sending practices, content quality, authentication setup (SPF, DKIM, DMARC), and recipient engagement.
Impact: Directly determines inbox placement with major mailbox providers like Gmail and Yahoo.
Action: Maintain a clean list, send relevant content, and ensure proper authentication.
Managing SpamCop blocks during warmup
If you encounter SpamCop blocks during your IP warmup, especially on a shared IP, the first step is to confirm the source of the blocks. Examine your bounce messages closely. If they explicitly mention SpamCop, it is likely an IP-level issue. Since you are on a shared IP, this points to the actions of other senders rather than your own immediate missteps.
The next crucial step is to communicate with your Email Service Provider. While SpamCop does not typically send direct complaints to ESPs, your ESP has access to the raw rejection messages and should be aware of any ongoing blocklist issues on their shared IPs. Politely open a ticket with your ESP, sharing the bounce information. They are responsible for monitoring and delisting their IPs from such blocklists. As mentioned by Acquia Campaign Studio, some ISPs block a sender domain if it appears on even one of the top blocklists.
Most importantly, do not let a SpamCop block completely halt your warmup. Mailbox providers that rely on their own sophisticated systems for reputation (like Gmail and Yahoo) are focused on your domain's sustained, positive sending behavior. Continue with your gradual sending increases, focusing on sending to engaged recipients, maintaining low complaint rates, and ensuring strong email authentication. This consistent positive activity will continue to build your overall sender reputation, which is far more influential than a temporary, isolated blocklist entry.
Blocklist Type
Primary Impact
Action to Take
SpamCop
IP-based blocks due to user spam reports. More impactful on smaller ISPs.
Contact ESP. Monitor own sending.
Spamhaus (SBL/XBL)
Widely used, significant impact on IP and sometimes domain reputation due to severe spam activity.
Urgent ESP contact and internal review of sending practices.
Barracuda
Primarily IP-based, often used by corporate networks. Can be sensitive to sudden volume increases.
Navigating an IP warmup, especially on shared IPs, requires patience and diligence. While encountering SpamCop blocks can be unsettling, it is often a temporary issue stemming from the shared nature of the IP rather than a direct indictment of your domain's reputation.
Continue to focus on sending quality, maintaining a clean list, and upholding strong authentication. Your consistent, positive sending behavior on your new domain will ultimately be the most significant factor in building trust with mailbox providers and securing strong inbox placement over the long term, even if you face minor hiccups along the way.
Views from the trenches
Best practices
Monitor all bounce responses closely to pinpoint the exact cause of rejections, especially during warm-up.
Maintain consistent sending volumes and engaged recipient segments, even if you encounter temporary blocks.
Proactively communicate with your Email Service Provider about any unexpected blocklist entries on shared IPs.
Common pitfalls
Panicking and abruptly halting your warmup schedule due to a shared IP blocklist entry.
Failing to analyze bounce codes, assuming all blocks are catastrophic for your domain reputation.
Not cleaning your email list before warming up, which can lead to more bounces and complaints.
Expert tips
When on a shared IP, accept that you have limited control over the IP's reputation; focus on your domain's reputation.
SpamCop blocklists generally have less impact on major mailbox providers, so keep building domain trust.
Ensure your authentication records (SPF, DKIM, DMARC) are correctly configured for your new domain.
Expert view
Expert from Email Geeks says that getting actual bounce responses helps make a better decision when unexpected statistics show up during a campaign.
December 1, 2024 - Email Geeks
Marketer view
Marketer from Email Geeks indicates that if all bounce responses are from SpamCop and they are on a shared IP, it is likely the issue is from another sender on that IP.
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
Yahoo) are focused on your domain's sustained, positive sending behavior. Continue with your gradual sending increases, focusing on sending to engaged recipients, maintaining low complaint rates, and ensuring strong email authentication. This consistent positive activity will continue to build your overall sender reputation, which is far more influential than a temporary, isolated blocklist entry.
