Is it harmful to send to unengaged users during email warmup, and how can I avoid spam traps and improve data quality?
Michael Ko
Co-founder & CEO, Suped
Published 27 Jun 2025
Updated 17 Aug 2025
9 min read
Email deliverability is a delicate balance, especially when you're warming up a new IP address or domain. The goal of email warmup is to establish a positive sending reputation with internet service providers (ISPs) like Gmail and Yahoo. This involves gradually increasing your sending volume to engaged recipients, signaling to ISPs that your mail is wanted. Introducing unengaged users into this process, particularly during the critical warmup phase, can be harmful. It's like inviting someone who doesn't know you well to a party where you're trying to make a good first impression. They might not show up, or worse, they might complain about the invitation.
When you send to unengaged contacts, you're essentially telling ISPs that a portion of your list isn't interested in your emails. This can lead to low open rates, high bounce rates, and increased spam complaints, all of which negatively impact your sender reputation. A poor reputation means your emails are more likely to land in the spam folder, even for your most engaged subscribers. This is especially true during a warmup period where you're trying to build trust from scratch. A single large send to a dormant segment could undo weeks or months of careful warming.
The danger is amplified by the presence of spam traps, which are email addresses specifically set up by ISPs and anti-spam organizations to catch senders with poor list hygiene. Sending to these addresses, even accidentally, can severely damage your reputation and lead to blacklisting (or blocklisting). Therefore, maintaining high data quality and employing robust list cleaning practices are not just good ideas, they are fundamental for successful email deliverability and avoiding such pitfalls.
The risks of emailing unengaged contacts
Sending to unengaged users, especially during a crucial warmup phase, presents significant risks to your email program. ISPs meticulously monitor how recipients interact with your emails. If your messages consistently receive low engagement (poor open and click-through rates), or worse, generate spam complaints, it signals to the ISP that your content is not valued by recipients, or that your list quality is poor. This directly impacts your sender reputation, making it harder for future emails to reach the inbox. It's been widely noted that sending to unengaged contacts can hurt overall deliverability by signaling low relevance to email service providers.
During email warmup, the objective is to demonstrate positive engagement patterns to ISPs, slowly building trust with your sending infrastructure and domain. A sudden influx of emails to a disengaged segment can drastically skew your engagement metrics, leading to a detrimental drop in sender score. This can trigger spam filters and result in your emails being diverted to junk folders or even outright blocked. My experience has shown that a large send to an inactive list, even a one-off, can undo months of painstaking warmup progress.
Beyond the direct impact on engagement rates, sending to unengaged contacts increases your risk of hitting spam traps. These hidden addresses are designed to catch senders with outdated or poorly managed lists. Hitting a single spam trap can be enough to severely damage your sender reputation, leading to immediate blocklisting (or blacklisting) and significant deliverability issues across the board. Understanding how spam traps work is crucial for any email sender.
Navigating the dangers of spam traps
Spam traps are a significant threat to email deliverability. They are email addresses used by ISPs and anti-spam organizations to identify senders who are not adhering to best practices. There are generally two types: pure spam traps and recycled spam traps. Pure spam traps have never been valid email addresses and are solely created for monitoring. Recycled spam traps were once legitimate email addresses that have become inactive and repurposed to catch senders who don't clean their lists regularly.
Hitting a spam trap signals to ISPs that your list hygiene is poor, potentially leading to your IP or domain being added to a blocklist (or blacklist). This can dramatically reduce your inbox placement, causing emails to be routed to spam folders or rejected entirely. The impact can be severe and long-lasting, making it incredibly difficult to reach your audience. For a more comprehensive understanding of these mechanisms, refer to our guide on email blocklists.
How to avoid spam traps
Consent based acquisition: Implement strict consent-based practices, such as double opt-in, where users confirm their subscription. This prevents bot sign-ups and ensures genuine interest.
Regular list cleaning: Regularly remove inactive or unengaged subscribers from your list. If a contact hasn't opened or clicked an email in 6-12 months, it's safer to remove them or attempt a re-engagement campaign.
Avoid purchased lists: Never purchase or rent email lists. These often contain high numbers of spam traps and unengaged addresses, leading to immediate deliverability issues.
Monitor bounces: Promptly remove hard bounces from your list. Hard bounces indicate invalid or non-existent email addresses, which can become recycled spam traps over time.
Strategies for improving data quality and deliverability
Improving data quality is not a one-time task, but an ongoing process fundamental to email deliverability. My approach emphasizes proactive measures to ensure your email list consists of engaged, legitimate subscribers. This starts at the point of data collection. Implementing a double opt-in process, for instance, verifies that subscribers genuinely want to receive your emails and helps prevent fraudulent or mistyped sign-ups from entering your list. This is a critical step in building a healthy sending reputation from the ground up, as detailed in this comprehensive guide.
Beyond acquisition, regular list cleaning is paramount. Unengaged subscribers not only inflate your list size with contacts who aren't interacting, but they also increase the risk of hitting spam traps. I advocate for a systematic approach to identifying and segmenting inactive users, attempting re-engagement campaigns, and then, if no response, sunsetting those contacts. This continuous process ensures that your sender reputation remains strong, as ISPs prioritize senders who send to engaged audiences. Our article on Gmail deliverability and list cleaning practices offers more insights.
Another crucial aspect of data quality is leveraging feedback loops and DMARC reports. These provide invaluable insights into how your emails are being perceived by ISPs and recipients, including spam complaints and authentication failures. Regularly monitoring these reports allows you to identify issues early and take corrective action, preventing long-term damage to your sender reputation. For example, understanding DMARC reports from Google and Yahoo can help you pinpoint problematic sending patterns.
List hygiene practices
Effective email list hygiene is vital for maintaining a strong sender reputation and ensuring high deliverability rates. It involves proactively managing your contact list to minimize risks and maximize engagement. Here's a breakdown of common practices:
Opt-in methods: Implement confirmed opt-in (double opt-in) where subscribers verify their email address. This ensures genuine interest and reduces the likelihood of spam traps.
Engagement segmentation: Segment your list based on engagement levels. Prioritize sending to your most active subscribers during warmup and for regular campaigns. For disengaged segments, consider re-engagement campaigns or removal.
Email warmup and unengaged users: a delicate balance
Email warmup is essentially a trust-building exercise with ISPs. The core principle is to demonstrate consistent, positive engagement from a new sending IP or domain by starting with low volumes of emails to highly engaged contacts and gradually increasing volume and list diversity. Introducing a large segment of unengaged users during this sensitive period, even for a critical, one-off communication, can be severely counterproductive. It undermines the very foundation of trust you are trying to establish.
If a critical message absolutely must reach unengaged users, and the risk to your main sending reputation is too high, consider isolating this send. One strategy I've seen success with is to use a completely separate, non-warmed IP address and a distinct subdomain for such broadcasts. This creates a buffer, ensuring that if the send to the unengaged list results in high complaints or spam trap hits, your primary sending reputation remains unaffected. While not ideal for regular operations, it's a pragmatic approach for unavoidable, high-risk sends. For more on managing large sends, see our guide on large sends without sufficient IP warmup.
Ultimately, the long-term health of your email program relies on a consistently clean and engaged list. Any deviation from sending to interested recipients, especially during warmup, carries a risk. Prioritizing careful list management and audience segmentation over short-term expediency will yield far better deliverability results. For effective strategies to avoid spam traps, our page on avoiding spam traps provides further guidance.
Views from the trenches
Best practices
Implement a double opt-in process for all new email subscriptions to confirm recipient interest.
Regularly segment your email list by engagement levels and prioritize sending to active subscribers.
Conduct re-engagement campaigns for inactive users before removing them from your main list.
Continuously monitor your bounce rates and promptly remove hard bounces to keep your list clean.
Utilize a dedicated IP or subdomain for critical, one-off sends to potentially unengaged lists.
Common pitfalls
Sending emails to lists that have not engaged in over 6-12 months can trigger spam filters and traps.
Relying solely on list validation software to detect all types of spam traps, as some can bypass them.
Purchasing or renting email lists, which often contain numerous spam traps and unengaged contacts.
Neglecting to remove hard bounces, which can negatively impact sender reputation over time.
Failing to adapt sending strategies during warmup periods, leading to reputation damage.
Expert tips
Good email collection processes are the primary defense against hitting spam traps.
Explicit permission for email subscriptions, not forced opt-ins, builds a healthier list.
Confirmed opt-in (double opt-in) is the most legitimate way to avoid spam traps.
List cleaning services may provide a false sense of security without addressing underlying data quality issues.
Focus on genuine engagement rather than trying to manipulate response rates with artificial warmup.
Expert view
Expert from Email Geeks says that sending to people who don't show any indication they want your mail is not a good introduction during warmup.
2024-04-26 - Email Geeks
Expert view
Expert from Email Geeks says that isolating mandatory broadcasts on a separate IP and subdomain can prevent damage to the main sending reputation.
2024-04-26 - Email Geeks
Summary and final thoughts
In conclusion, sending to unengaged users during an email warmup period carries significant risks that can derail your deliverability efforts. It can signal low relevance to ISPs, inflate bounce rates, and increase your chances of hitting damaging spam traps (also known as blocklists). The goal of warmup is to build a solid sender reputation based on positive engagement, and introducing disengaged contacts undermines this crucial process. Preventing deliverability issues and maintaining a healthy sending reputation requires a disciplined approach to list management and data quality.
To effectively navigate these challenges, I recommend prioritizing explicit consent, such as double opt-in, at the point of subscription. Regularly cleaning your email lists to remove inactive subscribers and hard bounces is also non-negotiable. While email validation services can help, they are not a substitute for fundamentally sound list acquisition and hygiene practices. Should a critical message necessitate reaching a potentially unengaged segment during warmup, consider the strategic use of a separate IP and subdomain to mitigate risk to your primary sending reputation.
By focusing on building and maintaining a highly engaged, clean email list, you not only avoid the pitfalls of spam traps and deliverability issues but also maximize the impact of your email campaigns. A strong sender reputation ensures your messages consistently reach the inbox, where they can achieve their intended purpose. Prioritize quality over quantity, and your email program will thrive.
Gmail and 
Yahoo. This involves gradually increasing your sending volume to engaged recipients, signaling to ISPs that your mail is wanted. Introducing unengaged users into this process, particularly during the critical warmup phase, can be harmful. It's like inviting someone who doesn't know you well to a party where you're trying to make a good first impression. They might not show up, or worse, they might complain about the invitation.
