How to avoid Gmail rate limits when sending essential communications to a large, infrequently mailed audience?
Matthew Whittaker
Co-founder & CTO, Suped
Published 23 Jun 2025
Updated 17 Aug 2025
8 min read
Sending essential communications to a large audience can be a critical task, especially when that audience is not mailed frequently. Many organizations face the challenge of needing to deliver important updates, policy changes, or compliance-related notifications to their entire user base, even if those users haven't received an email in months. This infrequent, high-volume sending pattern often triggers rate limits from major mailbox providers like Gmail. The result can be messages getting delayed, throttled, or even blocked, preventing your critical information from reaching its intended recipients.
The common error message you might encounter is 421-4.7.28 Gmail has detected an unusual rate of mail originating from your DKIM. This indicates that Gmail perceives your sending behavior as atypical for your domain, potentially signaling a security concern or a sudden change in volume that deviates from your usual patterns. Addressing this requires a nuanced approach that balances the need for broad reach with best practices for email deliverability.
Successfully delivering these essential communications requires careful planning and an understanding of how mailbox providers assess incoming mail. It's not just about the content, but also about the sending patterns and your domain's established reputation. Let's explore strategies to ensure your vital messages land in the inbox, not the spam folder or a deferred queue.
Understanding Gmail's rate limiting
Gmail, like other major mailbox providers, implements rate limits primarily to combat spam and ensure a high-quality user experience. When a domain suddenly sends a much larger volume of email than its historical average, it can trigger automated systems designed to detect unusual or potentially malicious activity, such as account compromises or phishing attempts. This doesn't necessarily mean your sender reputation is damaged, but rather that Gmail is being cautious.
The underlying principle is consistency. Mailbox providers build a profile of your sending behavior over time, including the volume, frequency, and engagement rates of your emails. A sudden deviation from this established pattern, especially a large spike to an infrequently mailed audience, can be flagged as suspicious. This is why Google advises senders to increase volume slowly to avoid issues.
It's important to differentiate between a temporary rate limit and a more severe deliverability problem. A temporary rate limit often resolves itself over a few hours or a day, but it signals that your sending strategy needs adjustment to avoid future disruptions. If you're consistently encountering these limits, it suggests your volume spikes are a persistent issue that could eventually impact your domain reputation and lead to more serious blocklisting (or blacklisting).
Strategic sending for infrequent audiences
When you have a large, infrequently mailed audience and need to send an essential communication, breaking up the send into smaller fragments over several days is a viable and often necessary strategy. This approach mimics the gradual volume increases that mailbox providers prefer, helping to mitigate the risk of triggering rate limits. It's a form of IP warming on a smaller scale, even if you're not using a new IP address. The goal is to avoid sudden spikes that alarm Gmail's filters.
Smart sending cadence
Determine your typical daily sending volume. If you normally send 10,000 emails per day and need to send to a list of 100,000, don't send all 100,000 at once. Instead, divide the total volume into manageable chunks that are gradually larger than your usual volume. For example, you might send 20,000 on day one, 30,000 on day two, and 50,000 on day three. This incremental increase signals to Gmail that your sending is legitimate and planned, rather than a sudden burst of potentially unsolicited mail.
The duration of the send-out depends on the size of your audience and your historical sending patterns. For very large lists that are rarely mailed, extending the send over a week or more might be necessary. This helps to spread out the impact and allows mailbox providers to recognize your domain's consistent, albeit increased, activity. It’s also crucial to monitor your deliverability during this period to catch any emerging issues early, such as throttling or delays.
List hygiene is paramount
Before initiating any large send, especially to an infrequently mailed audience, rigorous list hygiene is non-negotiable. Remove any unengaged, inactive, or bounced addresses. Sending to stale or invalid email addresses significantly increases your bounce rate and spam complaint rate, both of which severely damage your sender reputation. Even for essential communications, if a recipient hasn't engaged with your emails in a long time, their inbox might not be the best place for the message.
Technical considerations for deliverability
Beyond sending volume, the technical setup of your email program plays a crucial role in avoiding rate limits. Proper email authentication protocols are fundamental to proving to mailbox providers that you are a legitimate sender. This is especially true with the new Gmail and Yahoo sender requirements that went into effect in early 2024.
Email authentication
Ensure your SPF, DKIM, and DMARC records are correctly configured and aligned. A `421-4.7.28` error specifically mentions a DKIM issue, suggesting that Gmail is questioning the legitimacy of your sending domain. Implement a DMARC policy with a `p=quarantine` or `p=reject` to protect your domain from impersonation and to receive valuable feedback reports. A simple guide to DMARC, SPF, and DKIM is available for reference.
Monitoring and feedback
Utilize Google Postmaster Tools to actively monitor your domain's reputation, spam rates, and delivery errors. The dashboards provide critical insights into how Gmail views your sending. If you see elevated spam rates or consistent delivery errors, it’s a clear sign that adjustments are needed. Regular checks, especially after large sends, can help you detect issues before they escalate. An in-depth guide on Google Postmaster Tools can provide further assistance.
Here's a comparison of common sending pitfalls and best practices for large, infrequent audiences:
Common pitfalls
Sudden volume spikes: Sending to the entire list at once after a long period of inactivity often triggers Gmail rate limits.
Poor list hygiene: Including inactive or invalid addresses leads to high bounce rates and spam complaints.
Inconsistent sending: Lack of a regular sending pattern makes it difficult to establish a reliable sender reputation.
Reputation impacts
Temporary blocks: Messages are deferred or rejected with rate limit errors like 421-4.7.28.
Spam folder delivery: Even if delivered, emails might land in the spam folder, missing the inbox.
Blacklisting (or blocklisting): Severe or repeated issues can lead to your IP or domain being added to a blocklist.
Best practices
Gradual volume ramp-up: Break large sends into smaller batches over multiple days.
Thorough list cleaning: Regularly remove unengaged and invalid contacts to maintain a healthy list.
Consistent engagement: Aim for a more regular, albeit low-volume, sending schedule to engaged segments.
Higher inbox placement: Ensures your messages reach the primary inbox, not promotions or spam.
Reduced deferrals: Less chance of encountering rate limits or throttling issues.
Re-evaluating
While some communications are indeed legally mandated or absolutely essential, it's worth critically evaluating whether every email deemed "essential" truly requires a mass email to an entire, potentially unengaged, audience. Sometimes, the term "essential" is used broadly to include updates that could be delivered through alternative, less disruptive channels.
For example, terms of service (ToS) updates, privacy policy changes, or minor product notifications can often be displayed when a user next logs into your application or visits your website. If a user isn't engaging with your platform or services, sending them an email they don't want or need can negatively impact your sender reputation, leading to higher spam complaints and lower engagement metrics. This can impact your ability to reach even truly engaged recipients in the future.
Consider segmenting your audience and determining if the "essential" communication is truly relevant to everyone on your list, especially those who haven't opened an email in months or years. Sending to a list that hasn't been active, even with good intentions, can lead to hitting spam traps or generating high bounce rates, which will ultimately hurt your Gmail sender reputation.
Views from the trenches
Best practices
Maintain a consistent sending volume over time, even if it's low, to keep your sender reputation healthy with mailbox providers.
Segment your audience by engagement levels and send essential communications only to the most active subscribers.
Always clean your email lists regularly, removing bounces and inactive addresses before any large send to minimize negative feedback.
Implement strong email authentication (SPF, DKIM, DMARC) to prove your legitimacy and protect your domain's sending identity.
Common pitfalls
Sending large email volumes to an infrequently mailed audience without any prior warm-up can trigger immediate rate limits.
Neglecting to remove unengaged or invalid email addresses can lead to high spam complaints and blocklist (or blacklist) issues.
Assuming that "essential" communications bypass normal deliverability rules can result in unexpected throttling or blocking.
Ignoring Google Postmaster Tools warnings or DMARC reports means missing critical insights into your email performance.
Expert tips
If you must send a large, infrequent email, break it into smaller, manageable chunks and spread the send over several days, increasing volume incrementally.
Consider alternative communication channels for very old or unengaged contacts if the message isn't strictly legally mandated via email.
Actively monitor your bounce rates and spam complaint rates through Postmaster Tools, adjusting your sending strategy as needed.
Understand that getting rate limited occasionally doesn't necessarily damage your long-term reputation, but it signals a need for adjustment.
Marketer view
Marketer from Email Geeks says that if an audience isn't worth communicating with regularly, then it might be counterproductive to keep them on file and risk your sender reputation.
2024-10-22 - Email Geeks
Marketer view
Marketer from Email Geeks says that sending bulk mail to recipients only rarely tends to trigger temporary rate limits from Google.
2024-10-22 - Email Geeks
Key takeaways for reliable delivery
Navigating Gmail's rate limits when sending essential communications to a large, infrequently mailed audience requires a blend of strategic planning and technical diligence. While the instinct might be to send everything at once, a measured, incremental approach is almost always safer and more effective for deliverability.
Prioritizing list hygiene, implementing robust email authentication, and consistently monitoring your sender reputation are foundational practices. By adopting these strategies, you can minimize the risk of being rate-limited, ensuring your important messages reach their intended recipients without unnecessary delays or blocklisting (also known as blacklisting).
Gmail is being cautious.
Gmail's filters.
