How to improve Gmail deliverability after a decline in inbox placement?
Michael Ko
Co-founder & CEO, Suped
Published 16 Apr 2025
Updated 19 Aug 2025
9 min read
Seeing a dip in your Gmail inbox placement can be a frustrating experience. You've worked hard to build your list, craft your emails, and suddenly, your messages are landing in spam folders or not reaching the inbox at all. I've been there, and I know how challenging it can be to identify the root cause and implement effective solutions.
Gmail's filtering algorithms are constantly evolving, becoming more sophisticated in identifying unwanted mail. A sudden decline often points to shifts in your sending behavior, list quality, or even changes in how Gmail perceives your domain's trustworthiness. The good news is that with a strategic approach, it's possible to diagnose the problem and steer your emails back to the primary inbox. It requires patience and a commitment to best practices, but the effort is well worth it for your email program's health.
Utilise Google Postmaster Tools
The first step in recovering your Gmail deliverability is to understand what metrics Gmail is using to evaluate your emails. Gmail provides a powerful free tool called Google Postmaster Tools. If you're not already using it, you need to set it up for your sending domains immediately. It offers insights into your domain and IP reputation, spam rates, feedback loops, and authentication errors.
I often see senders overlook the importance of these dashboards. They provide direct signals from Google regarding your email performance. Pay close attention to your domain and IP reputation scores. A Bad or Low reputation indicates significant issues that need immediate attention, as your emails are likely being filtered to spam.
Additionally, check the spam rate dashboard. If your spam rate is consistently high, it tells you that recipients are marking your emails as spam, which severely impacts your deliverability. Identifying the specific campaigns or audience segments contributing to this high rate is crucial for targeted remediation.
Verify email authentication (SPF, DKIM, DMARC)
Authentication protocols are the bedrock of email deliverability, especially with the recent 2024 changes by Gmail and YahooMail. If your SPF, DKIM, and DMARC records are not properly configured or aligned, your emails are likely to be flagged as suspicious or even rejected. Think of them as your domain's passport for email sending.
SPF (Sender Policy Framework) lets recipients check that the email came from an authorized IP address. DKIM (DomainKeys Identified Mail) provides a way to verify that the email content hasn't been tampered with. DMARC (Domain-based Message Authentication, Reporting, and Conformance) pulls these together, telling receiving servers what to do if an email fails SPF or DKIM checks, and provides reporting. You can learn more about DMARC, SPF, and DKIM to ensure your setup is robust.
I've seen many cases where a simple misconfiguration in one of these records can lead to a significant drop in deliverability. Use a free email deliverability tester to diagnose any authentication issues. If you have Microsoft 365 or Google Workspacespecific DMARC issues, addressing them quickly is key to recovery. Always ensure your DNS records are correct and published.
Boost engagement and clean your lists
An engaged list is a healthy list, and this directly influences your Gmail inbox placement. If your subscribers aren't opening, clicking, or replying to your emails, Gmail's algorithms will interpret this as a lack of interest, leading to lower placement. Conversely, high engagement signals that your content is valuable and desired.
I recommend regularly cleaning your email list. Identify and remove or re-engage inactive subscribers. These are recipients who haven't opened or clicked your emails in a significant period, typically 90 to 180 days. Sending to unengaged contacts can increase your complaint rates and lower your sender reputation, which hurts your overall deliverability. It's better to have a smaller, highly engaged list than a large, unengaged one.
Consider implementing a re-engagement campaign for dormant subscribers before removing them. For instance, you might send a special offer or a re-permission email to those who haven't engaged in six months. If they still don't respond, it's time to let them go.
Positive engagement signals
Opens and clicks: Recipients interacting with your content, opening emails, and clicking on links.
Replies and forwards: Users replying to your emails or forwarding them to others.
Adding to contacts: Subscribers adding your sending address to their address book.
Moving to primary inbox: If emails are initially filtered to promotions, users manually moving them.
A key strategy for fostering engagement is to personalize and segment your audience. Generic, blast emails are far less likely to resonate. By breaking your list into smaller, more targeted groups based on demographics, interests, or past behavior, you can send content that is highly relevant to each segment. This leads to higher open and click-through rates, which in turn boosts your sender reputation and inbox placement.
Maintain consistent sending volume and content
Email volume consistency is another often-overlooked factor. If you send emails sporadically, or suddenly ramp up your volume significantly after a period of inactivity, Gmail's algorithms can view this as suspicious behavior. They prefer a steady, predictable sending pattern.
When recovering from a deliverability dip, I always advise a gradual approach to increasing volume, also known as IP or domain warming. Instead of immediately going back to your previous high send rates, start with a lower, consistent volume to your most engaged segments. Slowly increase the volume over several weeks, monitoring your Postmaster Tools dashboards for any negative trends. This signals to Gmail that you are a legitimate sender.
This consistent sending also applies to your content. Try to maintain a balance of content types and avoid sudden shifts from informational newsletters to heavily promotional emails. Varied content can also help prevent your emails from being consistently classified into Gmail's Promotions tab if your goal is the primary inbox. While the Promotions tab isn't the spam folder, many marketers aim for primary.
Inconsistent sending
Large volume spikes: Sending a very high volume after a quiet period.
Infrequent campaigns: Sending only once a month or less, making it hard to build consistent reputation.
Impact on deliverability
Higher spam flagging: Sudden changes can trigger spam filters.
Slower reputation building: Gmail struggles to assess consistent trustworthiness.
Even with the best intentions, your IP or domain might end up on a public or private email blacklist (or blocklist), especially after a period of poor sending practices. This is a clear signal to mailbox providers like Gmail that your emails could be spam or unwanted. While Gmail relies heavily on its internal filtering, being on an external blacklist (sometimes referred to as a blocklist) certainly doesn't help your case.
I always advise checking for blocklist (or blacklist) listings if you notice a sudden drop in deliverability. There are many tools available that allow you to check your domain and IP address against various blacklists. Understanding how email blacklists work is the first step in remediation.
If you find yourself listed, the delisting process varies depending on the blacklist, but generally involves fixing the underlying issue (e.g., stopping spam, cleaning your list), then requesting removal. Some blocklists (or blacklists) automate removal after a clean period, while others require manual requests. Continuous blocklist monitoring can help you catch issues early.
Refine content and list management
While fixing technical issues and cleaning your list are crucial, don't forget the content itself. Gmail's filters analyze email content for spammy characteristics. This includes excessive use of capitalization, exclamation points, spam trigger words, and suspicious links. Pay attention to your email's HTML size, too. For instance, emails over 102KB in HTML size can be truncated, potentially hiding your unsubscribe link and leading to more spam complaints.
A plain text version of your email is also important. Ensure that your HTML emails always have a corresponding plain text version, as some email clients or recipients may prefer or only be able to render plain text. Missing or poorly formatted plain text can negatively impact deliverability.
I also find that a clear and visible unsubscribe link is essential. Gmail now shows a “Manage subscriptions” button directly in the Gmail interface. Making it easy for subscribers to opt out prevents them from marking your email as spam, which is far more damaging to your sender reputation. Finally, ensure your sender name and domain are consistent and easily recognizable.
Views from the trenches
Best practices
Actively monitor your Google Postmaster Tools dashboards for reputation and spam rates.
Segment your audience and send highly relevant content to increase engagement metrics.
Implement a double opt-in process for all new subscribers to ensure list quality.
Regularly remove or re-engage inactive subscribers to keep your list clean.
Common pitfalls
Ignoring Google Postmaster Tools warnings about declining reputation or high spam rates.
Continuing to send to unengaged subscribers, which inflates list size but harms reputation.
Failing to implement DMARC or having authentication records that are misconfigured.
Drastically increasing email sending volume after a period of low activity.
Expert tips
Consider engaging subscribers through varied content, not just promotional emails.
If reputation is very low, a full re-permission campaign might be necessary.
Focus on the long-term health of your sending practices, not just quick fixes.
A gradual increase in sending volume to engaged users is more effective than rapid blasts.
Marketer view
Marketer from Email Geeks says they had good deliverability in 2018, then experienced a decline in Q4, and have been nursing their program back to health by significantly reducing send volume.
May 15, 2019 - Email Geeks
Marketer view
Marketer from Email Geeks says they can't definitively pinpoint where their deliverability problem is.
May 15, 2019 - Email Geeks
A path to improved inbox placement
Recovering from a Gmail deliverability decline isn't an overnight fix, but it is achievable. It requires a holistic approach that combines technical diligence, list hygiene, content optimization, and consistent monitoring. The key is to demonstrate to Gmail that you are a responsible sender who prioritizes user experience and sends valuable, wanted emails. By addressing the issues outlined above, you can systematically improve your sender reputation and ensure your messages consistently reach the inbox.
Remember, email deliverability is an ongoing process, not a one-time task. Regular monitoring, adaptation to new guidelines, and a commitment to providing value to your subscribers will keep your email program healthy and your inbox placement high.
Gmail and 
YahooMail. If your SPF, DKIM, and DMARC records are not properly configured or aligned, your emails are likely to be flagged as suspicious or even rejected. Think of them as your domain's passport for email sending.
Microsoft 365 or 
Google Workspacespecific DMARC issues, addressing them quickly is key to recovery. Always ensure your DNS records are correct and published.
