What are the best practices for sending a COVID-19 email to a large, unengaged list while preserving deliverability?
Matthew Whittaker
Co-founder & CTO, Suped
Published 8 Jun 2025
Updated 15 Aug 2025
8 min read
Sending a critical email, like a COVID-19 update, to a vast, unengaged email list presents a unique challenge for deliverability. While the urge might be to reach everyone with vital information, a sudden, large-scale send to recipients who haven't interacted with your emails in a long time can severely damage your sender reputation. This can lead to your emails being marked as spam, blocked by internet service providers (ISPs), and ultimately, not reaching the inboxes of even your most engaged subscribers.
The potential fallout includes higher bounce rates, increased spam complaints, and even getting your sending IP address or domain added to email blacklists (or blocklists). Once your domain is on a blocklist, it becomes significantly harder to get any emails delivered, impacting all future communications, not just the current one. Therefore, a careful and strategic approach is essential to mitigate these risks while still conveying your important message.
My goal is to outline a path that balances the immediate need to communicate with the long-term health of your email program. It involves a mix of strategic list management, content optimization, and a deep understanding of how ISPs evaluate incoming email volume and engagement.
The risks of a sudden, mass send
Attempting to send a sudden, massive volume of emails, especially to a list that hasn't been engaged, is like screaming into a quiet room. ISPs monitor sending patterns closely. A dramatic spike in volume, particularly from an IP or domain with a previously low sending frequency, immediately raises red flags. This can trigger spam filters, causing a significant portion of your emails to be diverted to spam folders or rejected outright.
Beyond the volume shock, an unengaged list often contains a high percentage of invalid email addresses, spam traps, and recipients who simply don't remember opting in. Sending to these addresses will lead to high bounce rates and spam complaints. Both metrics are critical indicators to ISPs about the quality of your list and your sending practices. High complaint rates can swiftly land your domain on various email blacklists (blocklists), making future email delivery almost impossible.
The risks of a sudden, large send
Sender reputation damage: ISPs will view the sudden, large volume and low engagement as suspicious activity, leading to immediate filtering.
Increased bounce rates: Many old addresses will be invalid or inactive, resulting in hard bounces, which harm your sender score.
Spam complaints: Recipients who haven't engaged in a long time are more likely to mark your email as spam.
Blocklisting: High complaints or spam trap hits can get your IP or domain listed on various blocklists.
This can quickly cascade into major deliverability issues. It's crucial to understand these risks before proceeding with any mass send to an unengaged list.
The long-term impact on your sender reputation can be devastating. Recovering from a damaged reputation, particularly if you end up on a significant blacklist (or blocklist), can take months or even longer. This means your regular, important emails will also suffer, affecting your ability to communicate effectively with your active audience.
Strategic segmentation and throttling
To mitigate the risks of sending to a large, unengaged list, the first step is always thorough list hygiene. This involves identifying and removing inactive subscribers, invalid addresses, and known spam traps. Even for urgent communications, a cleaner list significantly reduces bounce rates and spam complaints, both of which are critical for maintaining a healthy sender reputation.
Once your list is as clean as possible, segmenting your audience is paramount. Instead of sending to all 7 million contacts at once, prioritize your most engaged segments first. This could mean starting with subscribers who have opened or clicked an email in the last 30, 60, or 90 days. This strategy allows you to test the waters and build positive engagement signals before expanding to less active segments. This is a common strategy when dealing with large, inactive user lists.
Throttling your sends is another critical best practice. Instead of deploying millions of emails simultaneously, send in smaller batches over an extended period. This approach allows ISPs to gradually process your emails without perceiving a sudden, overwhelming influx. It also provides an opportunity to monitor real-time engagement and deliverability metrics, allowing you to pause or adjust your strategy if you see increasing bounce rates or spam complaints.
Problem: Unengaged lists
High risk of spam complaints: Recipients may not remember opting in or are no longer interested.
Increased bounce rates: Old lists often contain a significant number of invalid or deactivated email addresses.
Damaged sender reputation: ISPs penalize senders with poor engagement and high complaint rates.
Blocklist inclusion: Ending up on a blacklist can halt all email delivery.
Solution: Strategic approach
List hygiene: Clean your list to remove invalid and unengaged contacts before sending.
Throttling: Send emails in smaller batches to avoid overwhelming ISPs and maintain a consistent sending pattern.
Monitor metrics: Watch for bounces and complaints to adjust your sending strategy in real time.
Content relevance and recipient value
The content of your email is just as important as your sending strategy, especially when contacting an unengaged list during a crisis. It's crucial to evaluate if the email is truly necessary and provides undeniable value to the recipient. Is the information genuinely critical, or is it merely a broad announcement? Recipients are bombarded with messages, so yours must stand out for its relevance and purpose. According to Word to the Wise, ask if you can answer 'yes' to four key questions before launching your COVID-19 email campaign, ensuring its critical necessity.This advice on coronavirus emails is invaluable.
Your subject line should be clear, concise, and immediately convey the importance of the message without being alarmist or misleading. Avoid generic subject lines that might appear like spam. The email body should get straight to the point, clearly stating what the recipient needs to know or do. Use plain language and avoid excessive marketing speak.
Consider whether mentioning COVID-19 specifically impacts deliverability. While the general consensus is that mentioning COVID-19 in email content does not inherently cause deliverability issues, the surge in related emails during the pandemic did create a lot of noise. Your message needs to cut through that noise by offering real value.
Ultimately, every email you send should have a strong purpose and encourage interaction. Emails that elicit positive engagement signals, like opens, clicks, and replies, tell ISPs that your content is valuable and desired. Conversely, emails that lead to deletions without opening, or worse, spam complaints, negatively impact your sender reputation. Focus on delivering genuine value to your audience, especially during sensitive times.
Long-term list health and deliverability
Beyond the immediate crisis, maintaining long-term email deliverability requires consistent effort. Regular email list hygiene is not a one-time task but an ongoing process. Regularly remove inactive subscribers, hard bounces, and any addresses that consistently show no engagement. This proactive approach prevents your list from becoming a liability that drags down your sender score.
Consistent sending patterns also play a crucial role. ISPs favor senders who maintain a steady email volume and frequency. Sudden, drastic changes, either increases or decreases, can be perceived as suspicious. If you typically send 50,000 emails a week and suddenly send 7 million, it's a huge deviation that will raise flags. Building up your sending volume gradually over time, a process known as IP warming, is essential for new IPs or for significantly increasing volume.
Robust email authentication is non-negotiable for deliverability. Ensure your emails are properly authenticated with SPF, DKIM, and DMARC. These protocols verify that your emails are legitimately from your domain, preventing spoofing and improving trust with ISPs. A properly configured DMARC record, for instance, tells receiving servers how to handle emails that fail authentication, giving you control and visibility into potential abuse.
Finally, monitor your sender reputation proactively. Utilize tools like Google Postmaster Tools and other reputation monitoring services to track your standing with major ISPs. This allows you to identify and address issues before they escalate into major deliverability problems. Being vigilant about your email program's health is the key to consistent inbox placement.
Views from the trenches
Best practices
Start by validating your entire list to remove invalid addresses, which drastically reduces bounce rates and spam trap hits.
Segment your audience into highly engaged, moderately engaged, and unengaged groups, prioritizing the most active for initial sends.
Implement a gradual sending strategy, starting with small batches and slowly increasing volume while closely monitoring deliverability metrics.
Ensure your email content provides clear, concise, and valuable information that is truly necessary for the recipient to know.
Common pitfalls
Sending a massive, unthrottled email blast to an old, unengaged list, which will instantly trigger spam filters and reputation damage.
Ignoring list hygiene before a large send, leading to high bounce rates from invalid addresses and hitting spam traps.
Failing to segment the audience, treating all recipients the same regardless of their engagement history.
Sending generic or overly promotional content that lacks genuine value for a crisis communication, increasing spam complaints.
Expert tips
Communicate the deliverability risks to leadership in writing and ensure they acknowledge the potential consequences of a mass send.
If a full list send is unavoidable, consider the cost of professional list cleaning services to minimize immediate damage.
Develop a detailed rollout plan for re-engagement that includes multiple touchpoints and clear opt-out options.
Focus on content that genuinely serves the recipient's needs during a crisis, not just for the sake of sending an email.
Expert view
Expert from Email Geeks says a massive send to an unengaged list will devastate future deliverability, crushing the IP and sender reputation. It is critical to question whether the COVID-19 email is truly necessary.
2020-03-17 - Email Geeks
Marketer view
Marketer from Email Geeks says if you have a dedicated IP, a mass send might be possible, but it will require significant time afterward to recover deliverability due to opt-outs and inactive recipients causing spam complaints and bounces.
2020-03-17 - Email Geeks
Prioritizing long-term deliverability
Navigating the complexities of sending a critical email to a large, unengaged list, especially during a sensitive period, requires careful planning and a deep understanding of deliverability. While the immediate pressure to communicate widely can be intense, sacrificing your sender reputation for a single send can have long-lasting negative consequences on your entire email program. Prioritizing deliverability means prioritizing the ability to reach your audience effectively in the future.
The best approach involves a combination of rigorous list hygiene, thoughtful segmentation, gradual sending, and a strong focus on providing valuable, relevant content. By adhering to these best practices, you can maximize the chances of your important message reaching its intended recipients while preserving your long-term email deliverability and sender health. Remember, a healthy email program is built on trust and consistent positive engagement with your audience.
