Here’s how to make sure your emails don’t get lost in cyberspace.

Email deliverability is all about getting your messages where they’re supposed to go: the primary inbox. It measures how often your emails successfully land in front of your subscribers rather than being filtered into spam or blocked entirely.

Strong deliverability means more people see your messages, click your links, and convert. In this guide, we’ll walk you through what deliverability really means, what impacts it, and how to improve your inbox placement with the latest best practices for 2025.

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Key takeaways: email deliverability at a glance

To maintain strong deliverability:

• Authenticate your domain by setting up Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) records and implementing a Domain-based Message Authentication, Reporting, and Conformance (DMARC) policy, ensuring your emails are trusted and properly delivered. Google, Yahoo, and Microsoft require high-volume senders to authenticate their domains and make it easy for subscribers to opt out, so staying compliant is essential for inbox placement.

• Regularly clean your subscriber list to keep engagement high and avoid sending to inactive or invalid addresses.

• Avoid common spam triggers in your content, such as misleading subject lines, excessive punctuation, or too many hyperlinks.

• Monitor key engagement metrics such as open, click-through, and bounce rates to stay ahead of deliverability issues. 

• Aim for a deliverability rate of 99% or higher, and keep spam complaint rates below 0.10% to stay in good standing with mailbox providers.

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What is email deliverability?

Email deliverability is a holistic view of all the factors that impact whether messages ultimately get delivered. It’s closely tied to email engagement metrics and often mistaken for email delivery. Here’s how they differ:

• Email delivery indicates that the recipient’s mailbox provider has accepted the message. It confirms that the address is valid and that the server didn’t reject the message. But, it doesn’t tell you where the message landed—it could be in the primary inbox, spam folder, or somewhere else entirely.

• Email deliverability indicates whether a delivered message actually made it to a subscriber's inbox. It’s also a key performance metric for evaluating the effectiveness of your email marketing and measuring audience engagement.

To evaluate email deliverability, it’s important to monitor open, click, spam complaint, bounce, and unsubscribe rates, broken out by mailbox provider (e.g., Google, Yahoo/AOL, Microsoft).

Bottom line: If you focus on improving your email marketing deliverability, you can increase the likelihood of your emails landing in your subscribers' primary inbox.

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Why is email deliverability important?

You've invested a significant amount of time and energy into building a high-quality subscriber list and refining your strategy to effectively engage those subscribers. But if your emails don't reach their intended destination, your efforts won't be as successful. 

When you have low email deliverability rates, your subscribers can't click and convert from your emails, which can impact your program's overall ROI.

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What affects email deliverability?

Getting your emails to actually reach people isn't always straightforward. Email providers look at things like whether recipients open and click your messages, how you set up your email authentication, and your overall sending patterns. If you keep emailing people who haven't engaged in ages, providers might start thinking your emails aren't wanted and send them to spam instead.

Let’s take a deeper look at some of the key elements that affect deliverability:

• Sender reputation: Mailbox providers evaluate sender reputation using signals like IP reputation, domain history, sending consistency, and subscriber engagement. Strong performance across open rates, clicks, replies, and low spam complaints helps build trust over time. Sudden increases in email volume or inconsistent sending schedules can look suspicious and may hurt your reputation. Use a consistent “From” name and recognizable domain to reinforce trust and improve inbox placement.

• Authentication protocols: Mailbox providers rely on authentication protocols like SPF, DKIM, and DMARC to verify the legitimacy of sender domains. If you lack these safeguards—or they’re misconfigured—your emails might be rejected or mislabeled as spam.

• Email engagement metrics: Low open, click, and reply rates—or high bounce and unsubscribe rates—can cause your emails to be blocked or miss inboxes. Strong engagement metrics help mailbox providers recognize you as a trustworthy sender.

• Spam complaints: Email deliverability suffers a setback each time your messages are flagged as spam, making it harder for future emails to reach inboxes. Most platforms recommend keeping spam complaint rates below 0.10% to avoid triggering filters or harming your sender reputation.

• List quality: Continuing to email unengaged contacts can lower engagement and harm your sender reputation. Regularly clean your list to ensure it contains only active subscribers by removing inactive, outdated, and invalid addresses. 

• Email content: The content and structure of your emails plays a big role in whether they make it to subscribers' inboxes or if they’re doomed to the spam folder. Misleading subject lines, excessive punctuation, and messages overloaded with links and images can trigger filters.

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How do you measure your email deliverability rate?

Unlike email delivery rate (the percentage of emails accepted by a mailbox provider), email deliverability is tricky to figure out because mailbox providers don’t report on where accepted emails actually land. 

To gauge inbox placement, take a holistic approach by analyzing a combination of metrics, which include bounce rates, blocks, opens, clicks, unsubscribes, and spam complaints. Tracking these metrics over time and comparing them across providers can reveal where your emails may be underperforming. Benchmarking your performance against industry standards also helps determine whether these changes are specific to your program or reflect broader shifts among similar senders. 

Tracking deliverability metrics is crucial, but context matters. Some metrics might appear healthy at first glance, but they can be misleading if you don’t look at the full picture. For example, low spam complaint rates might suggest healthy inbox delivery, but if they’re paired with a drop in open rates, it could mean your emails are being filtered into spam, where subscribers never see them or can’t easily report them.

Some tools also run inbox placement tests with seed lists, which are test email addresses included in your campaigns to check how mailbox providers categorize your messages. While seed testing can offer helpful clues about inbox placement, it’s only a proxy indicator. Since seed addresses don’t open, click, or engage with your emails, they can’t reflect real-time subscriber behavior—one of the most important factors mailbox providers use to determine inbox placement. Use seed testing as one tool in your arsenal, not as your sole indicator of success.

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What is a good email deliverability rate?

Most senders aim for a deliverability rate of 99% or higher, indicating that their emails consistently reach inboxes without being blocked or labeled as spam. While 100% is ideal, it’s not always realistic, and small dips may point to opportunities to fine-tune your email program.

Here’s how deliverability rates are commonly interpreted:

• Excellent: (+98%): You’ve got a well-maintained list, strong engagement, and a solid sender reputation. Nearly all of your emails are reaching subscribers’ inboxes.

• Acceptable (95 - 97%): Some of your emails may be getting filtered into spam and other folders, likely due to minor authentication gaps or other small issues like outdated list segments.

• Needs attention (Below 94.99%): A significant portion of your emails are being blocked or filtered. High bounce rates, frequent spam complaints, and authentication issues are common culprits. 

Troubleshooting tip: If your deliverability rate declines, start by checking your bounce rate to see if you’re sending to invalid or inactive addresses. Review your spam complaint rate, which may indicate that your content or sending frequency isn’t resonating with subscribers. Then, verify that your SPF, DKIM, and DMARC protocols are correctly configured and aligned with your sending domain. These steps often uncover the root of deliverability issues and help you resolve them before they impact performance.

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New email sender requirements for 2025

Email service providers are constantly updating their sender requirements to make sure that only legitimate and trusted senders can deliver emails in high volumes. These rules are ever-evolving to help create safer, less spam-filled inboxes. 

Microsoft officially adopted sender authentication standards in 2025, following earlier updates from Google and Yahoo in 2024 that targeted high-volume senders. If you send more than 5,000 emails per day, these requirements apply directly to your program. They aim to enhance email authentication, simplify the unsubscribe process, and prevent unwanted emails from reaching consumers. 

Here's what you need to know (and do) to make sure your email marketing deliverability isn't impacted by these changes: 

Set up DMARC email authentication for your sending domain

Verifying the authenticity of the sender is crucial for maintaining email security. Mailbox providers rely on authentication protocols like SPF, DKIM, and DMARC to verify the legitimacy of sender domains.

Failing these checks can lead to your emails being marked as spam or not being delivered at all. That’s why it’s long been considered ‌best practice to configure these protocols. However, many high-volume senders fail to properly secure and configure their systems, making it easy for spam to go undetected among legitimate emails. So to address this issue, Microsoft, Google, and Yahoo have now made it mandatory for large senders to have a DMARC policy in place.

DMARC is like an extra layer of security for email authentication. It's all about making sure your emails reach their intended recipients and keeping your communication safe. 

With DMARC, senders can indicate whether their emails are protected by SPF, DKIM, or both (at least one of these methods is required to pass DMARC authentication). It also lets you set rules for receiving servers when an email fails SPF or DKIM authentication checks, such as sending those emails to spam folders or rejecting them altogether. 

If you don't already have a DMARC policy in place, it’s a good idea to set one up on your root domain.

Attentive has partnered with Red Sift, a leading DMARC and security vendor, to help our customers meet the minimum requirements set by Microsoft, Google, and Yahoo.

Always send emails “from” your own domain 

Microsoft, Google, and Yahoo now require senders to use their own domain in the “From” address of an email. The domain in the “From” address must also match the domain in your SPF or DKIM record. 

This requirement is part of the stricter authentication measures being implemented to enhance email security. It’s a necessary change considering many senders fail to adhere to this practice, resulting in a lack of proper authentication for their domains. When the “From” domain is inconsistent, mailbox providers struggle to determine the legitimacy of these emails and establish the sender's reputation. 

When you onboard your email program with Attentive, we provide you with DNS records to make meeting this requirement easier. These records enable us to authenticate your emails sent through our platform using DKIM and SPF, which, in turn, ensures that your emails are recognized as legitimate and trustworthy by mailbox providers. 

Let people unsubscribe from your emails with one click

Most of us have probably received some promotional emails that we're not particularly interested in. And when that happens, we want opting out to be simple. That's a big reason why Microsoft, Google, and Yahoo have also updated their email subscription policies, aiming to improve the user experience and reduce unwanted email. 

Google and Yahoo require senders who send more than 5,000 emails per day to include a one-click unsubscribe and honor opt-out requests within 48 hours. While not all mailbox providers have set a specific timeframe, treating two days as your standard is considered best practice to maintain compliance and avoid deliverability issues.

Avoid sending unwanted emails to keep spam rates low

When you send emails to subscribers who are unengaged or uninterested, it can lead to complaints or a lack of engagement. As a result, more of your emails may be classified as unwanted and end up in the spam folder. Not only is this frustrating for recipients, but it also costs mailbox providers time and resources to process and store those unwanted emails.

To improve the email experience for everyone, Microsoft, Google, and Yahoo have set guidelines that spam rates should be below 0.10% and never exceed 0.30%. This means that as a sender, it's important to be mindful of the content and recipients of your emails to avoid them being flagged as unwanted.

If you're an Attentive Email user, our Email Delivery Operations team will keep a close eye on your email traffic to ensure compliance with these guidelines (and work with you to improve your email program's deliverability, if necessary).

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How to improve email deliverability

Here are a few best practices to keep in mind as you continue to build your email marketing program. They offer insights into common issues, plus steps you can take to avoid them and improve your email deliverability. 

‍Segment and personalize your emails 

Mailbox providers prioritize email placement based on recipient engagement, which means low engagement rates can lead to your emails being filtered into spam folders.

Segmenting your email list and tailoring your content to appeal to different groups of subscribers can help make sure that your messages keep landing in the inbox. Think about building dynamic audience segments based on your subscribers’ behavior, such as their browsing and purchase history and previous engagement, as well as their product or category preferences. 

The more relevant and interesting ‌your content is, the more likely someone is to click, and the better your email deliverability will be over time. For example, a beauty brand that tailors messages around subscribers’ interests – like sending skincare promos to skincare shoppers – can drive stronger engagement and help future emails stay out of the spam folder.

Avoid common spam triggers 

Spammy language and content formatting can also trigger spam filters. That includes things like excessive capitalization or punctuation, misleading subject lines, or having too many hyperlinks. For example, a well-meaning subject line like “Don’t Miss Out! Your FREE Trial Is Waiting” will hurt deliverability by grabbing attention in all the wrong ways.

Here are some general guidelines to keep in mind when crafting your emails: 

• Write a clean subject line. Make it short and punchy, letting subscribers know what to expect so they'll want to open your email. Steer clear of words or phrases that could trigger spam filters (e.g., "free," "act now," "re:," "fwd:").
• Keep the formatting simple. Your emails should be easy to read, with the most important information at the top. Use a mix of images and text to get your message across, and include a strong call to action that encourages readers to click.
• Use hyperlinks sparingly. We recommend including no more than two or three links in your emails. Make sure all links are clearly clickable and have enough space around them so they're easy to click on mobile. 

Test and optimize your email strategy

To ensure your emails are engaging enough to land in the primary inbox, it's important to continuously test and refine them.

A/B testing different aspects of your email program can help you understand what works best for your audience (and what doesn't resonate with them as much). Then, you can use those insights to adapt your strategies accordingly. 

• Subject line: Your subject line is the gateway to your email. It's the first thing your subscribers see, and it's crucial for grabbing their attention. Experiment with the tone, style, and language in your email subject lines to figure out what gets your subscribers to open them. For example, if you typically use straightforward subject lines, test a version with a lighter, more conversational tone to see how your audience responds.

• Content: Once a subscriber opens your email, the content is what gets them to convert. Content includes your copy, images, call to action, and even the layout of your emails. A software company, for example, might see how an email that includes a product demo video performs against one that leads with a case study. Try testing these elements one at a time and comparing the performance to see which version performs better.

• Send time: Generally speaking, there are some best times to send an email, but every audience is different. We recommend A/B testing when you send your campaigns to determine which times or days of the week your subscribers are most engaged.

Remember, an email with a great subject line and engaging content—sent at the right time—is more likely to be interacted with, which signals to email providers that your messages are relevant and, in turn, enhances your deliverability. 

Keep your email subscriber list clean 

Sometimes subscribers who were once active can go cold, and the last thing you want is to keep sending emails to people who aren't opening them. That lack of engagement could affect your sender reputation. 

Regular list hygiene is one of the most important factors for long-term deliverability. That includes removing outdated contacts and disengaged users who are no longer interacting with your messages. Attentive automatically suppresses bounced emails, so if you’re migrating from another platform, be sure to carry over those addresses into your suppression list to avoid reintroducing known issues during warm-up.

Sunset segments and journeys in Attentive Email make it easy to identify and re-engage subscribers who haven’t opened or clicked on your emails in a while. You can also segment these inactive contacts and run re-engagement campaigns to give them a chance to opt in again before fully removing them.

You can even give these unengaged subscribers the option to opt out of your marketing emails altogether if they still aren’t responding after a few attempts to win them back. It may seem counterintuitive, but it's a smart move to increase your engagement rates.

Using a double opt-in process at sign-up can also help improve list quality and inbox placement. With double opt-in, subscribers confirm their email address by clicking a link in a follow-up message after signing up. This added step helps ensure your list only includes people who genuinely want to receive your emails, reducing the chance of fake, mistyped, or spam-trap addresses making their way into your database.

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How Attentive prioritizes email marketing deliverability

Monitoring for potential deliverability issues—low engagement rates, illegitimate addresses, bounces, and poor email formatting—is really time-consuming. If you’re an Attentive customer, you’ll get deliverability support every step of the way so you don’t have to do it yourself. 

We’ve intentionally built deliverability best practices into Attentive Email. With these tools and services—and a 99+% delivery rate—you can feel confident that your emails will make it to your customers' inboxes every time. We also have an expert team dedicated to managing relationships with mailbox providers, watching market trends, and monitoring your email activity to optimize performance. We measure open, click, spam complaint, bounce, and unsubscribe rates for each mailbox provider, so we can catch any issues early on and help preserve your sender reputation. 

Working with the right email service provider (ESP) is a critical first step in making sure your messages get where you want them to go. Learn more about Attentive Email and why it might be right for you today. 

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Frequently asked questions about email deliverability 

1. What is the difference between email deliverability and delivery?

Email delivery confirms that your message was accepted by the recipient’s server. Email deliverability tells you whether it actually reached the inbox or was filtered into spam.

2. What is a good email deliverability rate?

A strong deliverability rate is 99% or higher. Dropping below that range may point to issues like low engagement, poor list hygiene, or authentication problems that need to be addressed.

3. How can I improve email deliverability?

Begin by authenticating your domain with SPF, DKIM, and DMARC to ensure your messages are trusted. Focus on targeting subscribers who have recently engaged with your emails, since mailbox providers weigh recent interaction heavily when determining inbox placement. Maintain a clean list by removing inactive contacts, personalize your content to encourage clicks, and avoid formatting or language that might trigger spam filters.

4. Why are my emails not being delivered?

Emails often go undelivered due to authentication issues, outdated or invalid contacts, or high bounce and spam complaint rates. Low engagement or content that triggers filters can also keep messages from reaching inboxes.

5. What impacts sender reputation?

Mailbox providers look at factors like your IP reputation, domain history, sending habits, and engagement levels. High open and click rates, along with low bounce and spam complaint rates, help build trust and improve deliverability.