How Engagement Rates Impact Deliverability

Engagement rates are now the cornerstone of email deliverability. Email providers like Gmail and Outlook prioritize user behavior - such as opens, clicks, and replies - over traditional spam filters. Poor engagement can send your emails straight to spam, while positive interactions improve inbox placement.

Here’s what matters most:

• Replies are king. They signal trust and value to email providers.
• Spam complaints must stay below 0.1%. Anything above 0.3% triggers filtering issues.
• List quality is critical. High bounce rates (>5%) or inactive subscribers hurt deliverability.
• Technical setup matters. Proper SPF, DKIM, and DMARC configurations are non-negotiable.

To improve deliverability:

1. Focus on creating relevant, personalized content.
2. Maintain a clean, segmented email list.
3. Gradually warm up new domains or IPs.
4. Monitor sender reputation with tools like Google Postmaster.

The bottom line: Engagement builds trust with email providers, helping your messages reach inboxes and boosting ROI.

How Engagement Rates Affect Deliverability

The Move Toward Engagement Metrics

Mailbox providers like Google and Microsoft have shifted their focus when evaluating emails. Instead of primarily relying on IP addresses and domain history, they now emphasize recipient behavior - things like how long an email is read, clicks, replies, moving emails to folders, and adding senders to contact lists.

This means that simply sending a large number of technically flawless emails no longer guarantees they’ll land in inboxes. Providers use advanced language models to identify unnatural tones or mass-produced templates, making the quality of engagement more important than ever. These new standards build on earlier ideas about sender reputation, fundamentally changing what it takes to succeed in email deliverability.

Among engagement metrics, replies stand out as the strongest indicator of trust. When someone takes the time to respond to your email, it signals that your content is meaningful. Click-through rates also hold weight, but open rates have become less dependable. Thanks to Apple’s Mail Privacy Protection, automated pre-fetching can artificially inflate these numbers.

Positive and Negative Feedback Loops

The impact of these engagement metrics becomes clear when you look at feedback loops. Positive engagement - like opening, clicking, replying, or forwarding emails - creates a cycle that improves sender reputation. Internet Service Providers (ISPs) interpret these actions as proof that your emails provide value, which boosts inbox placement.

On the flip side, negative actions, such as deleting emails without reading them, unsubscribing, or flagging messages as spam, harm your reputation. This can lead to your emails being flagged as spam and missing the inbox entirely.

"Think about how you can make the user love your mails, rather than how to land in the inbox." - Gmail Postmaster

A great example of leveraging positive feedback loops is UniteSync, led by CEO Carlos Palop Moliner. In 2025, the company achieved an impressive 85.26% positive reply rate by crafting highly relevant messages for music creators. They also maintained strong domain health using Warmforge’s automated warm-up tools, allowing them to consistently avoid spam filters and reach key decision-makers. This success underscores how prioritizing recipient value over sheer volume can lead to compounding benefits over time.

What Drives Engagement and Deliverability

List Quality and Segmentation

Engagement starts with a well-maintained email list - one that avoids high bounce rates and minimizes spam complaints. If your bounce rate exceeds 2%, it’s a warning sign. Anything over 5% calls for immediate attention.

For example, in March 2023, Spotify tackled this issue head-on. Using Mailchimp's Verification API, they cleaned up their 45-million-subscriber list. In just 60 days, they cut their bounce rate from 12.3% to 2.1%. The result? Deliverability jumped by 34%, and they unlocked an extra $2.3 million in revenue.

Segmentation is where the magic happens. Instead of sending generic emails to everyone, divide your audience into smaller groups based on behaviors - like their last purchase or recent email interactions. This approach makes your emails more relevant. In fact, segmented campaigns can deliver 46% higher open rates and generate 760% more revenue compared to one-size-fits-all emails. Smaller, focused campaigns (50 recipients or fewer) also perform better, with response rates hitting 5.8%, while larger campaigns (over 1,000 recipients) see rates drop to just 2.1%.

"The best way to optimize email revenue per recipient is by refining your segmentation strategy."
– Randy McHugh, Founder, Stimulate Agency

Another effective tactic is implementing double opt-in. This ensures your list is made up of genuine subscribers. It can reduce hard bounces by up to 80%, while also naturally improving engagement since every subscriber actively confirms their interest. A strong list strategy like this lays the foundation for better deliverability.

Content That Drives Engagement

When it comes to email content, less is often more. Short emails - between 50 and 125 words - can achieve open rates as high as 42.67%. Personalized subject lines add more punch, increasing open rates by 26%. And here’s a fun fact: subject lines with exactly five words tend to perform 15.9% better.

Your call-to-action (CTA) is another key element. It should direct readers toward one clear, specific action. Including images can boost click-through rates by 42%, but make sure visuals enhance the message rather than overpower it. Avoid spammy elements like all-caps phrases ("FREE" or "URGENT") and keep your HTML styling clean and simple.

Go beyond just using first names in your emails. Personalizing content based on recent behaviors - like a product they browsed or an action they took - can increase open rates by 50% and drive revenue up to six times higher. The goal is to make each recipient feel like the email was crafted specifically for them.

Timing and Consistency

When you send your emails is just as important as what’s in them. A whopping 23% of opens happen within the first hour after an email is sent. To maximize engagement, aim for optimal times like Wednesday mornings between 7 and 11 a.m., or early afternoons on Mondays and Tuesdays around 1 p.m. Emails sent during business hours (9 a.m. to 6 p.m.) tend to perform well, with average open rates ranging from 44% to 46%.

"Timing your emails to coincide with your subscribers' peak activity periods is the key to increasing engagement and sending positive signals to ISPs."
– Evaldas Mockus, VP of Marketing, Omnisend

Consistency is critical for maintaining trust with Internet Service Providers (ISPs). Predictable sending patterns help establish a solid reputation, while sudden spikes in email volume can trigger spam filters. To keep your reputation intact, individual mailboxes should send no more than 30 to 50 emails per day. Over time, ISPs reward steady, reliable senders with better inbox placement. Combined with strong technical practices, these strategies ensure that your emails reach their intended audience.

Technical Setup That Supports Engagement

A solid technical setup is the backbone of ensuring high engagement rates lead to consistent inbox delivery. Without it, even the most engaging email content might never reach its audience.

Authentication Protocols (DMARC, SPF, DKIM)

Your email's visibility heavily depends on authentication protocols. SPF (Sender Policy Framework) specifies which IP addresses are allowed to send emails on behalf of your domain. DKIM (DomainKeys Identified Mail) ensures your message remains untampered by adding a cryptographic signature. DMARC (Domain-based Message Authentication, Reporting, and Conformance) ties these protocols together, instructing email providers on what to do if authentication fails.

Currently, 66% of senders use both SPF and DKIM, and DMARC adoption saw an 11% increase in 2024 compared to the previous year. Providers like Gmail and Yahoo mandate these protocols for bulk senders, meaning emails without them are destined for the spam folder.

"DMARC actually fills in a gap that SPF and DKIM both kind of left behind, introducing the concept of alignment… it closes that loophole and makes sure that you are who you say you are."
– Alison Gootee, Deliverability Advocacy Specialist, Sinch Mailgun

However, just setting up DMARC isn’t enough. Enforcing it with p=quarantine or p=reject is critical - monitor-only settings (p=none) leave your domain vulnerable to spoofing. Enforcing DMARC also qualifies you for BIMI (Brand Indicators for Message Identification), which allows your verified logo to appear in inboxes, boosting trust and open rates. Additionally, rotate your DKIM keys every 6 to 12 months. Alarmingly, 47.7% of senders only update keys after a security issue, leaving their domains exposed. With proper authentication in place, your infrastructure becomes the next line of defense for deliverability.

Email Infrastructure Solutions

Authentication alone won’t ensure deliverability without a strong infrastructure. Dedicated IPs are essential for maintaining control over your sender reputation. Shared IPs can be risky - if another sender on the same IP engages in poor practices, your deliverability can suffer. High-reputation IPs experience spam rates of just 4.1%, whereas low-reputation IPs see rates as high as 34.6%. Worse, when an IP gets blacklisted, 89% of emails sent from it fail to reach inboxes.

Platforms like Primeforge simplify this process by offering Google Workspace and Microsoft 365 mailboxes with automated DNS setup for DMARC, SPF, and DKIM. This eliminates manual errors that can trigger spam filters. Primeforge also provides US-based IP addresses, bulk DNS updates, and tools for managing multiple workspaces, making it ideal for scaling cold outreach efforts. Pricing starts at $45/month for 10 mailbox slots, or $38/month with annual billing.

The process of gradual warming is critical for new IPs or domains. Begin by sending 25 to 50 emails per day, gradually increasing volume to establish trust with ISPs. Distribute your sending across multiple IPs and domains to avoid sudden spikes that could flag spam filters. By combining proper authentication with a carefully managed infrastructure, you build the technical foundation needed to support both engagement and revenue growth.

Fixing Low Engagement and Deliverability Problems

When email engagement drops or messages start landing in spam folders, it’s time to act fast. Did you know that 1 in 5 emails never even reaches its intended recipient due to poor sender reputation? On top of that, 21% of opt-in emails fail to make it to the inbox. Rebuilding your sender reputation requires a mix of cleaning your email list, verifying technical setups, and sticking to consistent sending habits.

How to Recover Your Sender Reputation

The first step? Aggressively clean your email list. Get rid of hard bounces immediately and segment your subscribers based on their engagement history. Anyone who hasn’t opened or clicked in the past six months? Archive them. This simple move can protect your domain from being flagged by ISPs.

Once your list is clean, adopt a gradual warm-up strategy. If your domain or IP reputation has taken a hit, start small - send only 10 to 50 emails per day. Gradually increase your volume by 20% to 50% each week over a period of 3 to 6 weeks. Consistency is key: send 1–2 emails per week to each recipient rather than sporadic bursts, which can trigger spam filters. To monitor your progress, tools like Google Postmaster Tools or Microsoft SNDS can help track your reputation in real time. For a healthy sender reputation, aim for a mailbox health score of 97% or higher.

Don’t skip technical authentication. Make sure your SPF, DKIM, and DMARC records are properly configured. Platforms like Primeforge can simplify this process for Google Workspace and Microsoft 365, ensuring no manual errors derail your recovery. To further improve list quality, run win-back campaigns every quarter to re-engage inactive subscribers and use double opt-in for all new signups.

Once your reputation is back on track, focus on implementing long-term strategies to avoid repeating the same mistakes.

Preventing Future Deliverability Issues

To prevent future problems, authentication is a must. Starting in 2024, Gmail, Yahoo, and Outlook require SPF, DKIM, and DMARC (even at a minimum p=none) for bulk senders. By May 5, 2025, Outlook will also mandate strict authentication for domains sending over 5,000 messages per day. Ensure your domain alignment matches the visible "From" address to pass DMARC checks and build trust with ISPs.

Another priority is automated list hygiene. Set up policies to automatically suppress users who haven’t opened or clicked in six months. Run quarterly win-back campaigns to confirm who’s still interested. Keep in mind that email lists naturally shrink by about 22.5% per year, so regular maintenance is non-negotiable. A preference center can also help - let subscribers choose how often they want to hear from you and what kind of content they want. This reduces email fatigue and lowers unsubscribe rates.

"Organizations should make a point of setting up email validation, implementing a double opt-in at sign-up and automatically sunsetting any user who hasn't opened up one of their emails in the past six months."
– Kelly Hogan, Senior Director, Global Email Deliverability and Compliance, Braze

For added protection, use subdomain isolation to separate transactional emails from promotional ones. This ensures that reputation issues in one area won’t affect the other. Also, avoid using "no-reply" email addresses. Instead, opt for monitored inboxes that encourage two-way communication - this signals positive engagement to ISPs. Finally, secure your signup forms with CAPTCHA and real-time email validation APIs to block bots from inflating your list artificially.

Conclusion

As discussed earlier, evolving engagement metrics have significantly influenced email deliverability, making a strong infrastructure and effective list management more important than ever. Engagement rates - measured through opens, clicks, and replies - serve as a key indicator for ISPs to determine whether your emails belong in the inbox or the spam folder. High engagement enhances your sender reputation and improves deliverability, while poor engagement can send your emails straight to spam.

"Engagement is your lifeline to reputation as a sender. It is extremely important. If you think about what mailbox providers are doing, they want their users to get the emails they want to receive... And the way they do that is by looking at engagement."
– Nick Schafer, Sr. Manager of Deliverability & Compliance, Sinch

This insight underscores the importance of a solid technical and strategic foundation. Consistently landing in the inbox depends on three key elements: a reliable technical infrastructure, high-quality email lists, and ongoing monitoring. These practices, highlighted throughout this article, form a comprehensive strategy for improving deliverability. Prioritizing robust authentication protocols and regular list maintenance is essential for safeguarding your sender reputation.

To simplify the technical complexities, platforms like Primeforge provide tools to streamline the process. With features like automated DNS setup, US-based IPs, and multi-mailbox management, Primeforge allows you to focus on crafting personalized outreach. When paired with effective list management and targeted content, a strong infrastructure becomes the backbone of long-term deliverability success.

Email marketing offers the potential for an ROI of up to 4,200%, but that’s only achievable if your messages consistently reach your audience’s inbox. By prioritizing engagement, you can maximize your email marketing ROI and ensure your efforts truly pay off.

FAQs

How do engagement rates affect email deliverability, and how can I improve them?

Engagement rates play a big role in your email deliverability because they directly affect your sender reputation. To boost engagement, focus on personalizing your emails. Start by segmenting your audience - group them by industry, job role, or behavior. Craft subject lines that are clear, to the point, and tailored to their specific interests. And don’t forget to include a single, strong call-to-action that guides them toward the next step. Want to go the extra mile? Encourage replies by asking for feedback - this sends positive signals to email providers.

Another key step is maintaining a clean contact list. Remove bounced or inactive addresses, and don’t hesitate to cut those who haven’t engaged with your emails in the last 90 days. Aim for open rates above 15%, and keep your spam complaint rate below 0.1%. On the technical side, make sure your setup is rock-solid: configure SPF, DKIM, and DMARC protocols, and take time to gradually warm up new IPs to build trust with email providers.

If you’re doing cold outreach, having a dedicated email infrastructure can make a huge difference. Primeforge offers tools like US-based IPs, automated DNS setup, and mailbox profiling to simplify authentication and improve deliverability. With pricing starting at just $3.50 per mailbox, it’s a smart choice for teams that prioritize reliable cold-email performance. By combining personalized content, regular list cleanup, and a dependable email setup, you’ll not only increase engagement but also secure better inbox placement.

What are the key technical setups to ensure your emails land in the inbox?

To ensure your emails land in the inbox and not the spam folder, you need to have properly set up authenticated DNS records like SPF, DKIM, and DMARC. These records play a crucial role in verifying your email's legitimacy. On top of that, make sure your domains and mailboxes are correctly configured. Whenever possible, use automated DNS provisioning to streamline the process. Another key step is using dedicated or pre-warmed IP addresses, which help establish a strong sender reputation, improving your chances of reaching the inbox.

Platforms such as Primeforge can make this process much easier. They provide pre-configured email infrastructure, automated DNS setup, and handy features like US-based IP addresses and bulk DNS updates. These tools simplify maintaining high deliverability rates for your email campaigns.

Why are email replies the most important sign of engagement?

Replies are one of the clearest signs of strong email engagement because they represent an authentic, two-way conversation. When someone takes the time to respond, it indicates they trust your message and see enough value in it to engage further. This kind of interaction carries significant weight with mailbox providers when assessing your sender reputation and email deliverability.

In fact, mailbox providers treat replies as a key indicator that your emails are both relevant and welcome. By encouraging meaningful conversations through your emails, you can boost your deliverability and improve the chances of your messages consistently landing in recipients' inboxes.

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