Why does email engagement drop with Gmail on the 5th of each month?
Michael Ko
Co-founder & CEO, Suped
Published 5 Jul 2025
Updated 16 Aug 2025
5 min read
Many email senders experience fluctuations in engagement metrics, but a consistent drop around a specific date, like the 5th of each month for Gmail addresses, is particularly perplexing. It suggests a pattern that goes beyond typical deliverability challenges.
When facing such a consistent dip, the initial checks usually come up clean. Your IP and domain reputations might remain high, and there might be no preceding spikes in spam rates or bounces according to monitoring tools, including Google Postmaster Tools. This lack of clear signals can make troubleshooting especially frustrating.
The consistency of the drop, particularly for Gmail deliverability, points towards something systematic rather than random fluctuations. It implies a potential interaction with how Gmail processes or filters emails around that specific monthly mark.
Unraveling the monthly mystery
One of the first considerations for a highly consistent, recurring pattern like this is whether there are any hidden or unknown sending sources that might be active around the end of the previous month or the start of the current one. These could be sales teams using a separate service, rogue staffers, or even automated systems that you are not fully aware of. If these pushes occur, they might lead to a negative impact that manifests on or around the 5th.
To uncover such hidden sources, implementing DMARC with a reporting-only policy (p=none) is crucial. This setup allows you to receive DMARC aggregate reports that detail all senders using your domain, regardless of whether they are authorized or not. This can often reveal email streams you didn't know existed, which might be impacting your sender reputation (or domain reputation).
Another area to investigate is the possibility of a behavioral filter by Gmail. It’s theorized that Gmail, like other mailbox providers, might periodically test sender engagement or apply stricter filtering to certain segments or new subscribers on a rolling basis. If you're consistently introducing new contacts or sending to less engaged segments around the end of the month, Gmail might be evaluating that behavior, leading to a temporary drop. This is especially relevant if all engagement metrics are impacted, not just opens.
Proactive steps to take
Monitor actively: Use Google Postmaster Tools, DMARC reports, and your ESP's analytics to track deliverability closely, even when metrics seem stable.
Segment your audience: Isolate highly engaged recipients and consider sending to them separately during critical periods to insulate your main sending reputation.
Clean your lists regularly: Proactively remove unengaged or disengaged subscribers to prevent negative feedback loops with mailbox providers.
Gmail's dynamic engagement filters
Gmail's filtering systems are sophisticated and go beyond simple blacklists (or blocklists) or static sender scores. They heavily weigh recipient engagement and historical sending patterns. Even if your domain reputation in Postmaster Tools appears 'High', Gmail's internal algorithms might still be applying temporary filters if they detect behavior that deviates from expected engagement.
This could manifest as a periodic re-evaluation of your sending program. It's not uncommon for ISPs to adjust their filtering dynamically based on the recent behavior of both the sender and the recipients. A sharp, consistent drop in engagement for Gmail open rates on a specific date could indicate an automated system is flagging certain aspects of your sending, even if only temporarily.
The fact that all metrics are impacted, including opens and clicks, for both engaged and unengaged recipients, suggests a broad filtering action rather than an issue specific to content or list quality for a particular segment. This comprehensive impact supports the theory of a systemic filter or threshold being hit.
Given the consistency, one strategy to consider is proactively segmenting your audience and prioritizing your most engaged recipients on or around the 5th of the month. If the issue is related to Gmail testing engagement with broader segments, focusing only on your most active users during this period might help maintain a positive signal and short-circuit the pattern.
While this might not address the root cause, it could mitigate the immediate impact. Over time, if this strategy proves effective, it might help stabilize your engagement metrics and build a more consistent positive reputation with Gmail's algorithms. It's also critical to ensure that content relevance is always high, as email fatigue can set in, leading users to tune out even permissioned emails.
Beyond the 5th, consistent list hygiene, monitoring all email authentication protocols (SPF, DKIM, DMARC), and performing regular deliverability tests are ongoing necessities. Understanding if specific monthly events, like bill payments, benefit payouts, or internal reporting deadlines, could align with the 5th and trigger a change in recipient behavior or sending patterns is also worth considering, even if seemingly unrelated.
Monitoring area
What to look for
Actionable insights
Gmail Postmaster Tools
Reputation scores (IP and domain), spam rate, feedback loop data.
Identify drops, even minor, or shifts in user reports. Look for patterns around the 5th.
Authentication rates (SPF, DKIM, DMARC alignment), sources of mail.
Pinpoint unauthorized senders or authentication failures that may explain dips.
Engagement metrics
Open rates, click-through rates, unsubscribes, complaint rates.
Analyze trends by segment and date to isolate affected groups and content.
Views from the trenches
Best practices
Continuously monitor all available Postmaster Tools dashboards for any subtle changes.
Proactively segment your audiences based on engagement levels to optimize sending.
Regularly clean your email lists by removing unengaged or inactive subscribers.
Maintain consistent sending volume and frequency to build a stable sending history.
Common pitfalls
Over-relying solely on high IP/domain reputation without analyzing engagement trends.
Not using DMARC reporting to detect and address any unauthorized email senders.
Sending to large, unengaged segments, which can negatively impact overall sender reputation.
Ignoring subtle shifts in engagement metrics across specific dates or subscriber cohorts.
Expert tips
Implement DMARC with a p=none policy to gain comprehensive visibility into all email sources using your domain, as suggested by Email Geeks.
Test sending only to highly engaged users on problematic dates, such as the 5th of the month, to see if it circumvents the pattern, as advised by an Email Geeks marketer.
Investigate if any monthly internal or external business events, like billing cycles or monthly reports, align with the 5th and could inadvertently trigger changes in recipient behavior or sending volume.
Analyze how quickly your engagement metrics recover after the dip, as observed by an Email Geeks marketer, and adjust your list hygiene process accordingly.
Marketer view
Marketer from Email Geeks says they have experienced a sudden drop in email engagement, especially for Gmail addresses, consistently around the 5th of each month, with unique open rates falling significantly despite stable spam rates, bounces, and reputation.
2022-02-07 - Email Geeks
Expert view
Expert from Email Geeks says that Google Postmaster Tools is super useful for diagnosing deliverability issues and should be set up for all IPs and domains.
2022-02-07 - Email Geeks
Maintaining a healthy sending ecosystem
A consistent, monthly drop in Gmail engagement, particularly around the 5th, is an unusual but telling sign. It highlights the dynamic and often opaque nature of modern email filtering. While traditional metrics might not show immediate red flags, such a pattern suggests deeper interactions with Gmail’s sophisticated algorithms.
By meticulously reviewing all sending sources, leveraging DMARC reports, and adapting your sending strategy to proactively manage recipient engagement, you can begin to demystify these recurring dips. The goal is to not only recover quickly but to establish a sending pattern that consistently signals positive intent and high value to Gmail.
Gmail Postmaster Tools shows consistently 'High' domain reputation.
