Email Deliverability Essentials: How to Get More Emails into Your Recipients’ Inboxes

Email deliverability is the percentage of emails that make it to subscribers’ inboxes. This is separate from email delivery, which describes whether your email was successfully delivered to the receiving server. 

Since emails that end up in someone’s spam folder are still considered delivered, it’s possible to have good email delivery rates but poor deliverability. 

Many marketers ignore deliverability, but it has a significant impact on the success of your email marketing strategy. Put simply:

• High deliverability means your emails will land in front of more subscribers, as opposed to getting trapped in spam folders or blocked by firewalls. The result? More people open, read, click, and convert on your emails—so your email ROI increases.
• Low deliverability means your emails reach fewer subscribers. Naturally, your emails get less engagement, which further reduces your deliverability in a vicious yet avoidable cycle.

We’ll explain how email deliverability works, why it matters, and how to improve it. But before we dive in, here are two terms you need to know:

• Internet Service Provider (ISP): The companies that not only give people internet access but also provide mailboxes, like Gmail, Outlook, Comcast, and Yahoo. You can think of ISPs as gatekeepers.
• Email Service Provider (ESP): Tools marketers use to send emails to their subscribers. Think Mailchimp, Klayvio, Customer.io, and Drip.

Ready? Let's dive in:

• How does email deliverability work?
• How to improve your deliverability
• List hygiene
• Content optimization
• Email infrastructure
• Cheat sheet

How does email deliverability work? And why does it matter?

Good email deliverability enables your emails to actually land in recipients’ inboxes, something known as inbox placement. This journey isn’t as straightforward as you might think. Here’s what happens whenever you send a marketing email:

As of 2021, roughly 319.6 billion emails are sent per day, 45% of which is spam. 

To filter for spammers, ISPs rely on email sender reputation. Your reputation is the combination of your domain reputation, IP, and past sending performance, including factors like:

• The volume of email sent from your organization
• How many recipients mark your emails as spam or unsubscribe
• How often your emails encounter spam traps
• How many of your emails bounce
• How recipients interact with your messages, e.g., open, reply to, forward, click links, and delete

Different ISPs judge your sender reputation using their own algorithms, but there are a handful of third-party tools you can use to calculate your sender score. This is essentially a rating of your email sending habits on a scale of 1 to 100. The better your sender score and reputation, the more deliverable your emails are. 

Since not all recipients look at their spam or junk folders, email deliverability can make or break your email marketing strategy. 

With low deliverability, fewer recipients will see your emails and interact with them—meaning an even harder uphill battle when it comes to building long-term relationships with your subscribers. 

Achieving good email deliverability is just one step toward turning your subscribers into paying customers.

How to improve your deliverability

Remember that how recipients interact with your emails factors into your sender score and reputation. 

So if you're sending emails to people who genuinely want to receive them, you'll get more opens, clicks, and responses—and fewer unsubscribes and spam complaints. This improves your sender reputation and, in turn, your deliverability. Your emails wind up in more of your subscribers' inboxes.

But if you send your email list garbage, your sender reputation will suffer—and so will your email deliverability rates. 

The key to improving deliverability then is:

• Increasing email open rates and positive engagement signals (clicks, forwards, replies)
• Decreasing bounce rates, unsubscribe rates, and spam report rates

You can do this by adopting three broad strategies into your email strategy: practice good list hygiene; optimize your content; and choose quality email infrastructure. We’ll walk through each strategy and provide more detailed tactics below.

List hygiene

List hygiene refers to maintaining a list of subscribers who genuinely want to hear from you. To do so, prune your list regularly to get rid of inactive subscribers—the people who opted into your email list at some point but haven’t touched any of your messages in a long time.

Good list hygiene is critical. If your list’s packed with people who ignore your emails, your email metrics will suffer. 

Below are four tactics for good list hygiene:

• Collect emails ethically.
• Remove inactive contacts.
• Implement double opt-in.
• Make it easy for users to unsubscribe.

Collect emails ethically

We mentioned earlier that instead of reaching a recipient’s inbox, some emails fall into a spam trap. 

Getting caught in a spam trap signals to ISPs that you engage in some unethical email marketing behavior—like buying email lists or using harvesting programs to collect email addresses. 

So a simple way to improve your deliverability is to collect emails ethically. There are a few laws that you need to follow in order to maintain a healthy sender reputation:

• GDPR in the EU
• CAN-SPAM in the US
• CCPA in California
• CASL in Canada

Since your list might have subscribers from all regions, you should comply with all of them. Here are the most important considerations:

• Allow subscribers to control their data: GDPR affords rights to subscribers like the right to remove, change, access, and move their data. Your ESP has to support subscribers who want to make these requests, like with an email subscription management and preferences page. 

• Get consent: Ensure that everyone on your list explicitly opted in for marketing communication. That could be by implementing double opt-in, having subscribers provide written consent, or asking subscribers to check a box saying, "Yes, it's OK to market to me." 
• Never pay for email lists: It’s not ethical (or even legal) to email people who haven’t consented to receiving your emails. Even if it was, these users make poor recipients because they’re more likely to immediately delete your email (another strike for your sender reputation). Just don’t do it.

The best way to collect emails ethically? Focus on creating real value for users, like through free in-depth guides and resources. Then they’ll subscribe more willingly. 

You’ll build a list full of people who increasingly trust you, want to hear from you, and eventually buy from you.

Remove inactive contacts

It’s best practice to remove contacts who no longer engage with your emails. We recommend doing this quarterly.

Here’s how:

• Create a logical step in your email flow to identify subscribers who no longer engage with your emails. For example, people who haven’t opened in the last 90 days or across the last 5 emails.
• Using triggering logic, try re-engaging these inactive contacts with a win-back campaign—let them know they’ll be removed otherwise. If that fails, automatically remove them from your list. If you’d rather not remove them altogether, filter inactive contacts out of broadcast emails that you send frequently.

• Once you have a cleaned list, test a new campaign for higher open rate and CTR.

Ultimately, try to keep your unique open rates above 15% at minimum—but you should aim for double that. Our Growth Newsletter reaches a 46% open rate, which is possible due to our ongoing pruning.

Implement double opt-in

Most ESPs allow the options of single or double opt-in:

• Single opt-in means that anyone who subscribes in your email capture form or popup is immediately added to your list.
• Double opt-in means that subscribers are sent a confirmation email that they must click before they can be added to your list. 

We recommend double opt-in because it ensures that people truly want your emails. Another perk: it prevents fake email addresses and bots from getting added.

Make it easy for users to unsubscribe

Since they don’t engage with your emails, inactive subscribers are a deadweight for your email list. You can work on winning them back but some subscribers’ priorities may have simply shifted. So aside from pruning your email list quarterly, you should also make it easy for users to unsubscribe.

For example, let readers know how to unsubscribe, as we do at the top of each issue of our Growth Newsletter. 

Alternatively, give readers a very obvious way out, like Christopher Penn does in his newsletter. 

The bottom line here: Don’t hide your unsubscribe button—you want a list of people who want to hear from you. Not a list of people who don’t want your emails but can’t be bothered to find a hidden unsubscribe link.

Content optimization

The actual content and format of your emails also contribute to deliverability. How so?

Low-quality and irrelevant content fails to engage your email subscribers. They might unsubscribe or send it to the spam folder, increasing your complaint rates and deliverability issues in the long run. 

But remember: If you're sending quality emails to people who genuinely want to receive them, you'll get more engagement, which increases your sender score and deliverability.

On top of that, ISPs and email providers look for common patterns that help distinguish between legitimate emails and spammy content. For example, an excessive amount of links or adding false prefixes like “FW” and “RE” to subject lines often triggers spam filters. 

So the benefits of optimizing your messages’ actual content are twofold. Besides increasing the chances of your emails reaching users’ inboxes, it also creates a better email experience for your subscribers. Both of which get you more bang for every dollar spent on email.

Optimize for mobile

Since nearly 62% of email opens happen on mobile devices, creating mobile-first emails is a must. This makes it easier for people to engage with your messages, as opposed to clunky emails that are hard to read on a smartphone.

Fortunately, it's easy for email clients and ISPs to automatically adapt mobile-first designs to desktop. So if you optimize for mobile, your design will look sharp regardless of the device it’s seen on.

To create great mobile-first emails:

1. Choose a clean design that makes it easy for readers to consume. That means:

• Lots of negative space
• Big, legible fonts for both headers and body copy
• Large, contrasting CTAs

2. Use small files only. Many mobile devices run weak processors, meaning slower load times. Prevent people from bouncing by compressing your image files.
3. Avoid including too many images or too much HTML in your emails. One of the spam flags that you can avoid is the ratio of text to other content.
4. Send a test email and read it on your own phone before scheduling.

Delay your welcome email

Most marketers set up a welcome email automation that greets new customers immediately after signup. But people reflexively delete them without reading—a hit to your email metrics.

To get people to open and read your welcome emails:

• Delay your welcome email by 15 to 45 minutes. The time delay removes the subscriber's mental connection between their signup and your email. This bypasses the reflex to ignore.
• Set the email sender name to someone within your company, rather than your company’s name. People will be more likely to read your message.
• Write a unique subject line. Don't simply write "Thanks for joining!" Instead, write something that will make people want to click. Allbirds writes "Welcome to the Flock." Grammarly includes "You + Grammarly = Ready for Action."

Invite users to engage

Emailing is a two-way street. It’s not enough for your messages to just land in a recipient’s inbox. 

Besides opens and clicks, positive engagement metrics that benefit email deliverability include email forwards and replies.

So to improve your deliverability, invite users to engage. Here are a few techniques:

• Encourage users to share your email. This can be as simple as including a line somewhere like, “If you'd like to support our work, consider forwarding this email to a friend.” 
• Include a poll. Whether it’s about a fun or serious topic, a poll is an easy way to get users to engage—all it takes is a click. You can also leverage polls for quick insight on your audience; The Hustle does this with a poll that links to a short Google form. Alternatively, you can make it more casual like theCLIKK. Its poll options link to GIFs rather than a survey. 

• Prompt recipients to write back. Ahrefs does this from time to time with its weekly digests by asking readers something relevant to its niche. It makes this ask early in its email so that subscribers might respond regardless of whether they read the entire message.

Segment your email content

As your audience grows, so does the challenge of trying to create value for everyone.

Not every subscriber is looking for the same thing. As a result, some might lose interest in your emails and disengage.

To prevent this, segment your emails. This involves dividing your mailing list (usually automatically) into smaller groups to send more targeted messages. Doing so creates a more personalized experience for your audience. 

There are endless possibilities for how to segment your mailing list. Here are some examples:

• Level of engagement: Send more frequent emails to active subscribers who regularly engage with your messages, while scaling it back for those who don’t. Consider creating a re-engagement campaign to see if inactive subscribers are still interested, whether that’s by offering a reward or asking outright, “Do you still want to hear from us?”
• Sales funnel stage: Users who signed up for a product demo, free trial, newsletter, or a piece of gated content have different expectations for your marketing emails. Segment them based on how far along they are in the buyer’s journey.
• Purchase history: Looking at users’ past purchases, send emails about specific product categories and recommendations only to those who have a demonstrated interest in them. 
• User demographics: Any subscriber data you collect, like gender, location, and marital status, can be used for segmenting. For instance, you might send an announcement about an upcoming local conference only to users living in a particular region. 

Segmentation helps you send more relevant content that subscribers find valuable. Rather than ignoring them or moving them to spam, recipients will be more inclined to read your messages.

Email infrastructure

Email infrastructure is the hardware and software systems you rely on for your email marketing.

There are a lot of technical aspects to these systems, but the most important ones for deliverability involve using a professional email address, getting a dedicated IP, and authenticating your email. 

Fortunately, most reputable ESPs make it easy to handle these processes.

Use a company email address

The most effective email campaigns convey your authority to recipients. That means using a professional email address from a domain that you own.

Avoid sending emails from a free domain email address like Gmail, Yahoo, or Hotmail. Since ISPs recognize these as personal email addresses, they’re more likely to flag bulk emails from them as spam.

Also, remember to set your “from” email address as a real person’s name rather than your business name. An email from Julian Shapiro is more likely to get opened and read than an email from Demand Curve. It's more human.

One final consideration for your sender email: create a separate subdomain for the different types of emails you plan on sending. 

So if your usual email is jsmith@company.com, you could set up a subdomain and use jsmith@news.company.com to send only newsletters. This way, poor campaign performance won’t impact your main domain’s sender reputation.

For example, Nike uses email addresses that end in “official.nike.com” for its marketing campaigns while reserving “notifications.nike.com” addresses for password reset emails and other notifications.

This doesn’t only apply to your marketing campaigns—you can use subdomains for cold outreach and other campaigns.

Dedicated IP address

IP addresses are the strings of numbers used to identify a device on a network. 

The number of emails you send determines whether you should use a shared IP or a dedicated IP. 

• If you send less than 100,000 emails per month, stick with a reputable shared IP. 
• If you’re sending more than 100,000 emails per month, consider switching to a dedicated IP—and only if a marginal improvement in deliverability is high ROI for your business.

What’s the difference? By default, ESPs use the same IPs across multiple customers—these are shared IPs. With shared IPs, your deliverability is impacted by the other businesses using the same ESP. This usually isn’t a problem because reputable ESPs (like Mailchimp) have strict standards and remove businesses that spam.

But with a dedicated IP, you’ll have an IP that’s unique to your company, giving you more reputational control over your deliverability. Again, this isn’t necessary for companies sending fewer emails because they won’t have enough volume to build their own reputation.

Here are a few best practices for dedicated IPs:

• Warm up your IP address: Don’t immediately send out thousands of emails. Instead, start off by sending 200 emails and double volume each day (200, 400, 800, etc.).
• Use reCAPTCHA on your opt-in form: This prevents fake emails from bots getting onto your list, which inevitably leads to bounces.
• Use a Content Delivery Network (CDN): A CDN delivers your content faster regardless of geography. The asset is served from the data center that’s closest to the recipient. Additionally, ISPs let CDN content through the spam filters faster because it’s already trusted.
• Verify with a seed list testing tool: Seed lists enable you to see how your emails are inboxing (spam vs. inbox) across ISPs, before you send to your entire list.
• Friendly positive signal: Gather a list of friendly addresses across various ISPs. Then seed your reputation with positive engagement by asking these folks to open, click, reply, and mark your emails as important.

Email authentication

Whenever you send an email, ISPs check the IP address to see where it came from and to confirm that your IP has permission to send emails from your domain.
The point of this is email authentication, which helps ISPs prevent fraudulent email activity like phishing attacks. 

Email authentication is a must whenever you’re using an ESP to send messages on behalf of your custom domain. It involves a few protocols:

• Sender Policy Framework (SPF) lets senders define which IP addresses can send mail for a particular domain.
• DomainKeys Identified Mail (DKIM) attaches a digital signature to outgoing emails to confirm that messages aren’t fake or edited.
• DMARC builds off of SPF and DKIM for extra security. It lets email senders specify to receiving servers how to deal with emails that don’t pass the other methods of authentication—like send them to the junk folder or block them.

Some ESPs automatically provide authentication. For example, any domains bought through Mailchimp have DKIM enabled by default; but if you got your domain through another provider, you’ll need to set it up. Ultimately, how authentication works depends on your chosen ESP.

Fortunately, most ESPs offer clear instructions to walk you through the process. Here are resources from a few of the biggest ones:

• Mailchimp
• Campaign Monitor
• ConvertKit
• Customer.io
• Drip
• HubSpot
• Klaviyo
• Rejoiner

Cheat sheet

Remember that email deliverability can make or break your marketing strategy. 

So without solid deliverability, you’ll struggle to reach your audience. 

But when your deliverability rate is high, your emails will land in subscribers' inboxes, get more clicks and opens, and ultimately drive a higher ROI from your email marketing engine.

Below is a quick recap of our recommendations for improving it.

• Collect emails ethically—ask users for their consent and don’t buy email lists.
• Remove inactive contacts from your email list on a quarterly basis.
• Implement double opt-in.
• Make it easy for recipients to unsubscribe.
• Design and optimize your emails for mobile devices.
• Delay your welcome email.
• Invite users to engage with simple polls and prompts. 
• Segment your email list and create more targeted messages.
• Use a company email address and a real person’s name as your sender.
• For those sending more than 100,000 emails/month, get a dedicated IP address.
• Authenticate your emails for more security.