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Email deliverability: Everything you need to know to stay out of the spam folder

by Kate Lindemann  |  January 6, 2021

8 min. read
Gmail inbox on laptop screen.

It’s every email marketer’s nightmare: You create an amazing campaign full of stunning photos and clever copy and… nobody ever sees it. You’ve landed in the spam folder.

We’re all glad that spam filters protect us from unsolicited and nefarious emails. But your emails aren’t spam! So what went wrong?

In this article, we’ll go over the basics of email deliverability, so your campaigns end up where they belong: in your subscribers’ inboxes.

What is email deliverability?

Email deliverability refers to whether emails appear in subscribers’ inboxes. If emails are classified as spam, they bypass the inbox and go straight into the spam folder instead. Marketers can prevent this by using transparent, straightforward marketing practices and proper email configurations.

How email providers decide what’s spam

Each email provider uses a combination of criteria to decide which emails to deliver and which to send to the spam folder. These fall into three main categories:

Subscriber engagement – When subscribers open and read your emails, they’re vouching for you with their email providers. High engagement numbers show you’re sending quality content people want to receive. On the other hand, disengaged subscribers will harm your sender reputation, especially if they report your emails as spam.

Sender history – It’s hard to outrun a bad reputation. If your domain or IP address has a history of suspicious email activity, email providers will be wary of your campaigns.

Technical issues – Poorly configured emails will raise red flags. The same is true for emails containing deceptive links, hidden unsubscribe options and classically spammy language.

Spam folder in email client user interface.

It’s impossible to say exactly what combination of those factors it takes to land your domain in hot water with email providers. They don’t make those formulas public, since that would help spammers come up with ways to slip through their filters.

However, there are several near-universal best practices that will keep you safely within the bounds of email providers’ good graces. Let’s look at them now.

Best practices to avoid email deliverability problems

Build your list carefully

Adding people to a mailing list without their consent – or even worse, buying whole lists of email addresses – is a surefire way to make your engagement numbers plummet and get your domain blacklisted. The same goes for scraping email addresses from websites. To discourage this practice, some email providers lay ‘spam traps.’ Emails sent to these fake email addresses allow providers to see which senders are scraping addresses or buying mailing lists.

Screenshot of email sign-up pop-up form.

Avoiding these pitfalls is easy: Only email customers you already have a relationship with or people who signed up to a mailing list. Besides, emails will be more effective with a receptive audience anyway. Emailing people who don’t want to hear from you is a big risk without a reward.

Don’t give email providers the wrong idea

Attempts at deception are a handy shortcut for email providers to spot illegitimate emails. That means legitimate companies need to think about what might seem deceptive to an automated system. Here are some things to watch out for.

Avoid link shorteners

Spammers and scammers love link shorteners, because they hide a link’s true destination. Email providers want to see clear, accurate anchor texts that match what’s on the other side of the link. If you say you’re linking to a web shop, but the link leads to a totally different domain, providers might think you’re trying to trick people.

Choose a logical sender name

We can all be glad that email providers have measures in place to stop phishing emails that look like they came from your bank. But what do those filters mean for marketers?

Menu for customizing the sender field in an email marketing tool.

Some customization of the ‘From’ field is absolutely fine. A software company might label emails from support@company.com with their brand name. A fundraising plea from a non-profit’s CEO comes from a role account, not their personal email.

As long as the label makes sense for your domain, you’re in the clear. Just be careful not to think so far outside the box that email providers think you’re trying to hide who you are.

Write accurate subject lines

Spammers often use subject lines that start with RE: or FW: to make their emails seem like part of an ongoing conversation. Steer clear of this technique, or you might give email providers the wrong idea.

Email subject lines should make it easy to understand what’s inside the email. That’s not just good for email deliverability, it’s also a wise approach to customer communications generally.

Examples of descriptive email subject lines.

Use an email marketing tool with domain authentication

Use a reputable email marketing tool, so you can be sure that your email configurations and the technical infrastructure behind your campaigns are ironclad.

One of the most important configurations is domain authentication. Email marketing tools like Mailchimp use their infrastructure to send emails on your behalf. Authentication provides proof that they’re authorized to do so, preventing the appearance of a bait-and-switch. Any good email marketing tool will automatically embed these protocols in your emails, so you don’t need to worry about them.

Keep your subscribers happy

Email providers use spam filters to provide a better experience for their users. If you’re sending content people want to click and read, they’ve no reason to filter it out. That’s why subscriber engagement plays a crucial role in sender reputation. When subscribers click and open your emails, they’re providing positive feedback and signaling that your content is legitimate.

Screenshot of Gmail's report spam button.

Email recipients also have the opportunity to provide negative feedback in the form of the ‘mark as spam’ button. Too many spam reports will deal a massive blow to your sender status.

Spam reports pose a danger even to companies that build their mailing lists honestly. People who aren’t tech-savvy don’t always know how easy it is to unsubscribe from a mailing list. If they click their email provider’s ‘mark as spam’ button instead, your sender reputation could take a hit.

How do you keep engagement numbers high and spam reports to a minimum? Here are some top tips for keeping your subscribers happy:

Use double opt-in

Double opt-in requires new email subscribers to confirm their email address by clicking a link in a confirmation email. This allows you to verify that new subscribers are real, preventing bounces and spam reports from fake addresses.

Email from Chipotle requesting email verification as part of a double opt-in processes.

Make it easy to unsubscribe

A clearly marked unsubscribe link at the bottom of each email is a legal requirement in many parts of the world. But even if it weren’t, it’s still a best practice. With no other way out, subscribers who no longer want to get your emails would otherwise be forced to reach for the spam button.

Plus, because clicks and opens are measured as percentages, a smaller list will boost your engagement numbers.

Email footer with bright red unsubscribe link.

Focus on high-quality content

Sending emails subscribers want to receive is at the core of any good email marketing strategy. Relevant, interesting emails will boost your engagement numbers, help your sender reputation and convert better.

Need some inspiration? Check out our top tips for email newsletters.

Use segmentation and automation to send more relevant emails

Even with great content, providing a good experience to all your subscribers at once can be a challenge. That’s because not all emails are relevant to everyone. Segmentation and automation offer a way to create a more customized email experience.

Illustration of marketer sitting on a laptop, sending three different emails to different subscribers.

Email segmentation is when you group your contacts by category, making it easy to tailor campaigns to different types of subscribers. Mailing lists can be segmented according to any criteria, including customer status, location and more.

Email automation provides an even higher level of personalization. Automated emails go out to individual subscribers as a result of a certain action or trigger, like a purchase or abandoned cart. The result is a highly tailored email experience that always feels personalized and relevant.

Practice good list hygiene

A little email list management will go a long way to protecting your sender reputation and boosting your engagement rate.

Go through your mailing list on a regular basis to remove any inactive accounts, especially hard bounces. Hard bounces are emails that can’t be delivered, because the address is no longer active. Too many failed deliveries will harm your sender reputation, so it’s important to remove these addresses from your list.

Illustration of marketer engaging in email list management by cutting email addresses that bounce from his mailing list.

Stay on the right side of the law

Laws like the CAN-SPAM Act and Europe’s General Data Protection Regulation (GDPR) turn many email best practices into legal requirements. Make sure you’re familiar with the laws that apply to your area. Keep in mind that if you have subscribers in different jurisdictions, you might need to comply with multiple laws.

Don’t worry, you’ve got this

With high stakes and so many factors involved, email deliverability can seem like an intimidating topic at first. But in reality, the best practices for email deliverability are the same as the best practices for email marketing generally.

Optimizing for deliverability isn’t about gaming a system. If your campaigns are honest, transparent and going out to a legitimate contact list, you’re already on the right path.

Keep the best practices we’ve gone over in the back of your head, and you can turn your attention to the fun part of email marketing: designing creative campaigns your customers will love.