What Is Email Deliverability and How to Increase Your Deliverability Rate?

‍What Is Email Deliverability and What Are Its Key Metrics?

Email deliverability means ensuring that your email messages reach your audience’s inbox and avoid the spam folder. It’s not just about delivery—where the recipient’s server accepts an email—but about landing where it counts.

High deliverability is achieved when your emails arrive and effectively engage the audience. This is achieved by fostering trust with inbox service providers (ISPs) and your audience. 

Deliverability is influenced by the sender’s reputation, the quality of the email content, and the recipient’s engagement with previous messages. 

A high deliverability rate ensures your audience sees your emails, driving higher engagement and ROI for your campaigns.

Let’s look at the key metrics:

• Open rate: The percentage of people who open your email, reflecting engagement.
• Click-Through Rate (CTR): The number of recipients who clicked on links in your email.
• Bounce rate: Emails that couldn’t be delivered. Soft bounces are temporary issues, while hard bounces indicate invalid addresses.

What Is the Inbox Placement Rate and Why It Matters

Inbox Placement Rate (IPR) is the percentage of emails sent successfully to the recipient’s primary inbox instead of being filtered into the spam folder, promotions tab, or other locations. 

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While the delivery rate simply tracks whether the recipient's server accepts an email, IPR focuses on where the email ends after delivery.

Inbox placement is essential for at least three reasons: 

• Visibility and engagement: Emails in the primary inbox are more likely to be seen, opened, and acted upon. 
• Accurate assessment of campaign success: A high delivery rate might need to be more precise if many of those emails end up in spam. IPR offers a clearer picture of campaign performance by showing how many emails reach the recipient’s attention.
• Impact on ROI: High inbox placement ensures better engagement rates, translating to improved click-throughs and conversions and, ultimately, a better return on investment (ROI) for email campaigns.

How to Calculate the Effectiveness of an Email Campaign Using IPR

Here’s how to analyze campaign performance using IPR as a factor:

• Engagement metrics correlate. A higher IPR indicates overall campaign success, leading to more opens and clicks.
• Benchmarking campaign performance. Comparing IPR across campaigns will help you identify strategies or issues affecting inbox placement.
• Optimizing future campaigns. Tracking IPR over time is one factor that helps improve list segmentation, content quality, and sending habits.
• Diagnosing deliverability issues. A low IPR indicates that deliverability improvements, such as better list hygiene or enhanced sender reputation, are needed.

Factors That Influence Email Deliverability and Inbox Placement Rate

• Sender reputation. Think of it as your email credit score. Spam complaints, high bounce rates, and inconsistent sending schedules can damage your reputation. A good reputation leads to more emails being flagged as spam, increasing IPR. Pro Tip: Use tools like Google Postmaster to monitor your sender's reputation.
• Engagement metrics. ISPs monitor how recipients interact with your emails. Higher open rates, click-through rates, and replies signal to ISPs that your emails are relevant, improving IPR. Positive engagement signals (opens, clicks, replies) help maintain a stellar sender reputation, while negative signals (spam complaints, bounces) can hurt your deliverability. Focusing on email volume, send frequency, and content quality can further optimize inbox placement.
• Quality of email content. Spammy keywords, misleading subject lines, or poorly formatted emails can trigger spam filters, lowering IPR. Even technical details, like using URL shorteners, might trigger spam filters. Personalization, compelling subject lines, and clear calls-to-action (CTAs) are essential for driving engagement and improving deliverability. Including interactive elements, such as polls or surveys, can further boost engagement. Regularly analyzing engagement metrics and adjusting your strategies based on the data will help you maintain strong inbox placement over time.
• Email list quality. Avoid buying email lists or failing to validate your subscriber addresses. Using outdated or purchased email lists increases the likelihood of bounces, spam complaints, or hitting spam traps, which hurt inbox placement. Spam traps are email addresses set up to catch spammers. They identify senders with poor list hygiene. 
• Proper email authentication. Proper email authentication using protocols like SPF, DKIM, and DMARC builds trust with ISPs and increases the chance of landing in the inbox.
• Email volume and sending frequency. Bombarding subscribers with too many emails can lead to fatigue and higher unsubscribe rates, while inconsistent sending schedules may reduce recipient recognition and engagement. 

The Role of Sender Reputation and IP Address Reputation 

Email deliverability depends heavily on sender reputation and IP address reputation, which ISPs and ESPs evaluate to decide whether your emails reach inboxes or spam folders.  

Sender Reputation

Sender reputation works like a credit score—better scores mean higher deliverability. ISPs assess it based on recipient engagement, bounce rates, and complaint rates.  

•   Use permission-based lists to ensure recipients want your emails.  
•   Clean your list regularly to remove inactive or invalid addresses.  
•   Avoid spammy practices like misleading subject lines or over-promotion.  

IP Address Reputation

ISPs track IP address reputation to determine email legitimacy.  

• Shared IPs: Cost-effective but risky—other senders’ actions can harm your deliverability.  
• Dedicated IPs: Offer full control and better reliability but require consistent volume to maintain reputation.  

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‍IP Warming

When using a new dedicated IP, gradually increase email volume over weeks to build trust with ISPs. Start with engaged subscribers and monitor metrics like open rates and bounces.  

Sender Reputation and IP Address Reputation  Best Practices

• Monitor reputation using tools like Google Postmaster Tools or Sender Score.  
• Authenticate emails with SPF, DKIM, and DMARC to build trust.  
• Maintain list hygiene to avoid bounces and complaints.  
• Send consistently to avoid spam filter triggers.  
• Partner with an ESP that supports shared and dedicated IPs effectively. 

10 Best Practices to Boost Email Deliverability

Follow these strategies to stay out of the spam folder.

1. Maintain a Clean Email List: List Building and List Hygiene Best Practices 

• Enable double opt-in. Confirm with subscribers that they want to receive your emails. This will reduce spam complaints and ensure higher-quality subscribers.
• Remove invalid addresses. What is worse than sending an email to a dead inbox? Keep practicing removing unknown users and hard bounces. Over time, email addresses become outdated, or people change their contact details. Regularly validating your data and eliminating invalid or incorrect contacts keeps your list clean and your email deliverability high. 
• Track engagement. It’s crucial to track how subscribers are interacting with your emails. Are they opening them? Clicking links? If a contact hasn’t engaged in a while, it may be time to remove them from your list or move them to a re-engagement campaign. Holding onto disengaged users hurts your metrics. Re-engage these users with campaigns like “You didn’t open any of our recent emails. Should we not bother you anymore?” Implement a sunset policy for non-responsive users. This reduces the chances of being marked as spam and improves overall performance.

How to Manage Emails with Bounces and Spam Complaints

• Hard Bounces: Immediately remove invalid email addresses.
• Soft Bounces: Retry delivery or review server configurations to resolve issues.
• Track spam complaints and address them promptly to reduce negative impacts.

2. Authenticate Your Emails

Email authentication ensures that Internet Service Providers (ISPs) and email systems verify your emails as legitimate. Authentication protocols act as digital gatekeepers, helping ISPs differentiate between genuine emails and spam or phishing attempts. Let’s break down the key protocols and why they matter:  

• SPF (Sender Policy Framework): Verifies that your emails are sent from authorized servers. SPF is a protocol that specifies which mail servers are authorized to send emails on behalf of your domain. When an email is sent, ISPs check the SPF record of the sender’s domain to confirm that the message originated from an approved source. Without SPF, malicious actors can spoof your domain—sending fraudulent emails that appear to come from you. A failed SPF check can cause your emails to be flagged as spam or rejected outright, damaging your email deliverability.  
• DKIM (DomainKeys Identified Mail): Ensures the email content hasn’t been altered during transit. It adds a digital signature to your email headers, which ISPs can validate using a public encryption key published in your domain’s DNS. If an email fails validation, DKIM indicates that the email was altered after it was sent, which is a red flag for ISPs. Passing DKIM checks builds trust with ISPs, ensuring your messages reach the inbox rather than being filtered into spam.  
• DMARC (Domain-based Message Authentication, Reporting, and Conformance) ensures that your emails pass SPF and DKIM checks.  DMARC allows you to specify how ISPs should handle emails that fail SPF or DKIM checks—whether to reject, quarantine, or allow them. Aligning SPF and DKIM policies is designed to provide greater email security.  It helps protect your domain from spoofing and phishing attacks while enhancing your email’s reputation with ISPs. A strong DMARC policy demonstrates to ISPs that your emails are secure, improving deliverability. DMARC policies also generate reports, giving you insights into unauthorized activity on your domain.

3. Segment Your List

Segmenting allows you to send targeted, relevant content to smaller groups of subscribers, boosting engagement and reducing spam complaints. It matters because personalized messages lead to higher engagement, lower unsubscribe rates, and stronger customer loyalty. So, consider tailoring your content to speak directly to each segment’s needs.

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4. Optimize and Personalize Email Content

• Avoid spammy phrases like “Act Now,” “Congratulations,” or excessive use of exclamation marks.
• Avoid generic subject lines.
• Avoid “no-reply” addresses. 
• Personalize emails to increase engagement. Use the recipient’s name and tailor content to their preferences. A personalized “from” name can also increase open rates.
• Adhere to the 80/20 rule, balancing promotional and value-driven content.
• Ensure a proper text-to-image ratio; too many images can trigger spam filters.
• Use GIFs and CTAs sparingly, ensuring quick email load times.
• Avoid adding malicious code: remove JavaScript, Flash, dynamic scripts, or unauthorized attachments. 
• Add alt text for images, test your code for compatibility across email clients, and provide a web version.
• Include a clear and visible unsubscribe link. Complex unsubscribe processes lead to spam complaints.
• Test different subject lines email designs, and send times to identify what works best for your audience.

5. Test Before You Send

Preview how your emails render across devices and test for spam scores. Pre-send testing can catch issues before they harm your campaign. Consider using testing and tracking tools like Google Postmaster, Yahoo Feedback, and Microsoft SNDS.

6. Implement IP Warming

When using a new IP address, gradually increase your email sending volume. This helps build trust with ISPs and prevents your emails from being flagged as spam. 

7. Use BIMI (Brand Indicators for Message Identification)

BIMI displays your logo next to your email in inboxes, enhancing trust and brand recognition. It’s a great way to stand out.

8. Stay Compliant with Privacy Laws

Implement permission-based subscriber acquisition practices. Use compliant opt-in processes like double opt-in to validate consent. It's critical to only add contacts who have opted in to receive your communications. This not only ensures compliance with privacy laws, like GDPR or CAN-SPAM but also means you're engaging with people who are genuinely interested in what you offer. A smaller, highly engaged list is far more valuable than a large, disinterested one.

Make sure your opt-in process aligns with GDPR and other regulations. A compliant list isn’t just ethical—it’s essential for deliverability.

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9. Avoid Spam Traps

Avoid purchasing email lists, which often contain spam traps and unengaged recipients. Validate your email list regularly to ensure it doesn’t include unknown users or recycled addresses. Spam traps are email addresses that are expressly set up to catch spammers, and there are two types: pristine spam traps and recycled spam traps. Pristine traps are new and never used for legitimate sign-ups, while recycled traps are old addresses that were once active but are now abandoned. Avoid both by regularly cleaning your list and only sending to contacts who’ve genuinely opted in. If you hit these traps, it can seriously damage your sender's reputation.

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‍10. Throttle Your Sending

Send large email campaigns over time to avoid being flagged by spam filters. This is particularly useful during holiday promotions or big launches.

Evolving Spam Filters and Their Impact on Deliverability

Spam filters continue getting more sophisticated.  In 2025, they use advanced algorithms to analyze multiple dimensions of an email’s quality and legitimacy. Being a way to protect recipients from unwanted or harmful messages, they are a real challenge for marketers. A failure to meet the evolving criteria of spam filters can severely hurt your email deliverability. Here’s how:

• Comprehensive authentication checks. Spam filters rely on sender authentication protocols like SPF, DKIM, and DMARC. Emails that fail authentication checks are red-flagged as potentially fraudulent and are often blocked. 
• Engagement metrics and quality signal. Spam filters assess how recipients interact with your emails. Engagement data, such as open rates and click-through rates, are used to determine their value. If recipient often deletes your emails without opening them or mark them as spam, that is a signal to filter that your content lacks relevance or credibility. Over time, low engagement rates can cause your emails to land in spam folders.
• Content and formatting analysis. Filters scan email content for excessive spam trigger words, overuse of capitalization or punctuation (like exclamation marks), poor image-to-text ratios, or the absence of plaint-text versions. Even a well-intentioned email can appear spammy if design and language trigger content-based triggers. 
• Sender reputation tracking monitors your sending behavior and factors such as bounce rates, complaint rates, and sending frequency. Frequent spam complaints indicate poor targeting or irrelevant content, and erratic or excessive email campaigns can be flagged as suspicious. A poor sender reputation can result in your emails being deprioritized, throttled, or blocked entirely by ISPs.
• Domain reputation and blacklists. Spam filters also evaluate your domain reputation. Being associated with a blacklisted domain or IP address significantly lowers deliverability. Sending emails from free domain addresses (e.g., Gmail, Yahoo) will also hurt your deliverability. Evolving filters cross-check your domain against real-time blacklists. Even one flagged campaign can tarnish your reputation, affecting future deliverability.
• User preferences and feedback loops. Spam filters take user preferences seriously. If users frequently unsubscribe, ignore your emails, or mark them as spam, filters adapt to deprioritize your emails across similar audiences. Personalization, segmentation, and relevance are a must. Generic or untargeted campaigns increase the risk of negative feedback, which spam filters use to block your emails.

Wrapping It Up

If you aim for a deliverability rate of 95% or higher, prioritize list hygiene, strong authentication, high-quality content, and consistent engagement.

Email deliverability is a dynamic and critical part of marketing. By focusing on engagement, maintaining a clean list, and leveraging the right tools, you’ll keep your emails out of the spam folder and in front of your audience. Start auditing your email list, set up authentication protocols, and implement these best practices.