Here's everything you need to know about email deliverability, what influences inbox placement, and how to measure the health of your email program.
Email deliverability determines whether your emails reach your subscribers' inboxes instead of being filtered into spam. When your emails reach the inbox, they have the opportunity to drive engagement, clicks, and conversions.
Mailbox providers like Gmail may organize inbox messages into tabs such as Primary or Promotions, but successful deliverability is about reaching the inbox in the first place. In this guide, we'll explain what email deliverability is, why it matters, what influences inbox placement, and how to measure the health of your email program.
Key takeaways: Email deliverability at a glance
To improve email deliverability and maximize inbox placement:
- Authenticate your sending domain. Configure SPF, DKIM, and DMARC so mailbox providers can verify your identity and trust your emails. Authentication is now a baseline requirement for high-volume senders and plays an important role in inbox placement.
- Keep your subscriber list healthy. Regularly remove invalid, inactive, and unengaged contacts to maintain strong engagement signals and protect your sender reputation.
- Create emails people want to engage with. Clear subject lines, relevant content, and thoughtful formatting encourage opens and clicks while reducing the likelihood of spam complaints.
- Monitor the metrics that matter. Track engagement, hard and soft bounce rates, unsubscribes, and spam complaint rates—ideally by mailbox provider—to identify issues early and understand how your program is performing.
- Protect your sender reputation over time. Strong deliverability is the result of consistent sending practices, healthy subscriber engagement, and keeping spam complaint rates below 0.10%. Together, these signals help mailbox providers recognize you as a trusted sender.
What is email deliverability?
Email deliverability is a measure of how successfully your emails reach—and are seen in—your subscribers' inboxes. It reflects the overall health of your email program, including the factors that influence inbox placement, such as sender reputation, authentication, subscriber engagement, and list quality. It's closely tied to email performance metrics and is often confused with email delivery. Here's how they differ:
- Email delivery indicates that the recipient's mailbox provider accepted the message. It confirms that the email address is valid and the server didn't reject the message—but it doesn't tell you where the message landed. An email that's delivered could end up in the inbox, spam folder, or another mailbox category.
- Email deliverability indicates whether a delivered message reaches the inbox, where subscribers have the opportunity to see and engage with it. It's also a key measure of your email program's health because mailbox providers use engagement signals, authentication, and sender reputation to determine future inbox placement.
To evaluate email deliverability, monitor metrics like open rates, click rates, spam complaints, bounces, and unsubscribes—ideally broken out by mailbox provider (for example, Gmail, Yahoo, and Microsoft).
Bottom line: Improving email deliverability increases the likelihood that your emails reach your subscribers' inboxes instead of being filtered into spam. The stronger your sender reputation and subscriber engagement, the better your chances of consistent inbox placement.
Why is email deliverability important?
Email deliverability directly impacts the performance of your email marketing program. If your emails don't reach the inbox, subscribers don't have the opportunity to open, click, or act on your messages—no matter how relevant the content is.
Strong inbox placement helps you get more value from every campaign by giving subscribers more opportunities to engage with your brand, supporting stronger conversion rates, and maximizing the return on the time and effort you've invested in your email program.
What affects email deliverability?
Getting your emails to reach the inbox isn't always straightforward. Mailbox providers evaluate a combination of signals—including authentication, sender reputation, subscriber engagement, and sending patterns—to determine whether your messages belong in the inbox. If you continue emailing subscribers who haven't engaged in a long time, mailbox providers may interpret those messages as unwanted and filter more of your emails into spam, reducing the impact of your campaigns and limiting revenue opportunities.
Here are some of the biggest factors that influence email deliverability:
Sender reputation
Mailbox providers evaluate sender reputation using signals like IP reputation, domain history, sending consistency, and subscriber engagement. Strong open rates, clicks, replies, and low spam complaint rates help build trust over time. Sudden spikes in email volume or inconsistent sending schedules can look suspicious and hurt your reputation. Using a consistent "From" name and recognizable sending domain also reinforces trust and supports stronger inbox placement.
Authentication protocols
Mailbox providers rely on authentication protocols like SPF, DKIM, and DMARC to verify that your emails are legitimate. If these records are missing or misconfigured, your emails may be rejected or filtered into spam.
Email engagement
Mailbox providers use subscriber engagement as an important signal when evaluating your email program. Declining open rates, clicks, and replies—or increasing bounce and unsubscribe rates—can indicate that your emails aren't consistently reaching the inbox or aren't resonating with subscribers. Monitoring these trends can help you identify deliverability issues before they have a larger impact.
Spam complaints
Every time a subscriber marks one of your emails as spam, it sends a strong negative signal to mailbox providers. Higher spam complaint rates can damage your sender reputation and make future inbox placement more difficult. Most mailbox providers recommend keeping spam complaint rates below 0.10%.
List quality
Continuing to email inactive or invalid contacts can lower engagement over time and weaken your sender reputation. Regularly removing unengaged subscribers and invalid email addresses helps maintain a healthier list and supports stronger inbox placement.
Email content
Your email content and formatting can influence deliverability, but not because specific words automatically trigger spam filters. Misleading subject lines, excessive punctuation, or emails overloaded with links and images can reduce trust with subscribers, increasing the likelihood of spam complaints and weaker engagement. Over time, those negative signals can make it harder for future emails to reach the inbox.
How do you measure email deliverability?
Unlike email delivery rate (the percentage of emails accepted by a mailbox provider), email deliverability can't be measured with a single metric because mailbox providers don't report exactly where accepted emails are placed.
Instead, evaluate inbox placement by looking at a combination of metrics, including hard and soft bounce rates, opens, clicks, unsubscribes, and spam complaints. Tracking these metrics over time—and comparing performance across mailbox providers—can help you identify potential deliverability issues and understand where your email program may need attention. Benchmarking your performance against industry standards also helps you determine whether changes are unique to your program or reflect broader trends.
No single metric tells the whole story. For example, low spam complaint rates may seem like a positive sign, but if they're paired with declining open rates, it could indicate that more emails are being filtered into spam, where subscribers never have the opportunity to engage.
Some tools also use inbox placement testing with seed lists—test email addresses included in campaigns to see how mailbox providers categorize messages. While seed testing can provide helpful insights, it's only one piece of the picture. Because seed addresses don't open, click, or otherwise engage with emails, they can't replicate the real subscriber behavior that mailbox providers rely on when determining inbox placement. Use seed testing as one tool in your arsenal, not as your sole indicator of success.
What are good email deliverability benchmarks?
A strong email program is measured by more than just deliverability. While most senders aim for a delivery rate (emails accepted by mailbox providers) of 99.5% or higher, it's equally important to monitor engagement and sender health metrics that influence long-term inbox placement.
Here's how key email metrics are commonly evaluated:
These benchmarks provide a useful snapshot of your email program's overall health, but it's important to evaluate them together rather than in isolation. Mailbox providers look at multiple signals when determining inbox placement, so a change in one metric often tells only part of the story.
For example:
- Click rates are highly contextual. Not every subscriber clicks through directly from an email. Some may visit your website later or through another channel, so use click rates as one indicator of engagement—not the only measure of success.
- Unsubscribes aren't always a negative signal. While no one wants to lose subscribers, healthy unsubscribe activity can indicate that your emails are reaching the inbox. It also helps remove subscribers who no longer want your messages, which can strengthen engagement over time and support a healthier sender reputation.
Measuring your email program is only half the equation. Once you understand what's working—and where improvements are needed—you can start taking steps to strengthen inbox placement over time.
What’s next
Now that you understand what email deliverability is, what influences inbox placement, and how to measure the health of your email program, it's time to put that knowledge into action.
Our guide to How to Improve Email Deliverability walks through the strategies that have the biggest impact on sender reputation and inbox placement—from authentication and list management to segmentation, testing, and ongoing optimization.
Read next: How to Improve Email Deliverability: Best Practices for Better Inbox Placement
Frequently asked questions about email deliverability
1. What is the difference between email deliverability and email delivery?
Email delivery confirms that a mailbox provider accepted your message. Email deliverability measures whether that message reaches the inbox, where subscribers have the opportunity to see and engage with it. A delivered email can still be filtered into spam or another mailbox category, which is why deliverability is the more meaningful measure of email program health.
2. What is a good email deliverability rate?
A healthy email program looks beyond delivery rate alone. While most senders aim for a delivery rate of 99.5% or higher, it's also important to monitor engagement metrics like opens, clicks, spam complaints, and bounce rates. Looking at these metrics together provides a more complete picture of your sender reputation and inbox placement.
3. How can I improve email deliverability?
Start by authenticating your sending domain with SPF, DKIM, and DMARC so mailbox providers can verify your identity. Then focus on sending relevant emails to engaged subscribers, maintaining a healthy email list, monitoring key deliverability metrics, and regularly testing and optimizing your email program. Together, these best practices help strengthen sender reputation and improve inbox placement over time.
4. Why are my emails not reaching the inbox?
Emails may miss the inbox for several reasons, including authentication issues, poor sender reputation, outdated or invalid email addresses, high spam complaint rates, or low subscriber engagement. Reviewing your deliverability metrics can help you identify where issues may be occurring and determine the best path forward.
5. What impacts sender reputation?
Mailbox providers evaluate sender reputation using a combination of signals, including domain and IP reputation, authentication, sending consistency, subscriber engagement, spam complaints, and bounce rates. Building trust over time through relevant content, healthy list management, and consistent sending practices helps support stronger inbox placement.
6. Does landing in the Promotions tab mean my email has poor deliverability?
No. For many marketing emails, landing in the Promotions tab is expected and still counts as successful inbox placement. Mailbox providers like Gmail first determine whether an email belongs in the inbox or spam. If it's accepted into the inbox, it may then be organized into tabs like Primary or Promotions based on the recipient's settings and the type of message. The goal of email deliverability is to consistently reach the inbox—not necessarily the Primary tab.
