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8 best practices to improve email deliverability

Gabija Trimbel Gabija Trimbel
· 18 min read · Email marketing · May 25, 2021

We all want the same thing – emails delivered directly to the inbox every time. With a few tweaks to your email practices, you’ll be set up for optimal deliverability.

While email deliverability can seem complex because of all the variables that affect your email’s inbox placement, there are a few simple things that you can do to improve your own deliverability dramatically.

In this article, we’ll cover 8 email marketing deliverability best practices so you can optimize newsletters to reach the inbox while maintaining a healthy email list.

A common misconception about your open rates is that it’s all about the subject line. The truth is that opens are more connected to the sender’s name.

When the recipient sees a familiar name or brand that they like, they will open it regardless of the subject line. Think about the emails you receive from your best friend. The subject line can be blank and you’ll open it.

Spam filters are trying to figure out if you really know your subscribers. By using your real name or a consistent brand name in all your emails, your open rates will improve, your spam complaint rate will decrease, and the email providers will send your emails to the inbox.

improve email deliverability - personalize sender email address

In addition to a recognizable sender name, use a real email address that people can reply to if they want. Email addresses with real names and an authenticated domain name, such as, tend to have better deliverability rates.

Finally, avoid using domains like,, etc. for your email campaigns. Ironically, they are usually blocked by Gmail or Yahoo themselves.

To make your life easier and avoid deliverability issues, you can set up a default sender email address in MailerLite. This setting will add the same address every time you create a new newsletter. Here are the instructions to set a default sender.

In the same way you show someone your ID card to prove you are who you say you are, domain authentication is a way to let the email providers (Gmail, Outlook, etc.) know that it’s you sending emails from your address.

The process to authenticate your domain is not super technical, but it requires that you know where you bought or registered your domain address (your URL). These are companies like GoDaddy, Bluehost and WordPress.

Once you know where your domain is registered, you’ll need to provide them with two important pieces of information that you can get from your MailerLite account:

  1. Sender Policy Framework (SPF) - Gives your email marketing tool (MailerLite) permission to send email messages on your behalf and confirms that you are the owner of the domain’s email address.

  2. Domain Keys Identified Mail (DKIM) - Ensures that the content in your newsletters was not changed during the sending process.

Here is a quick video tutorial on where to find these two items (SPF and DKIM) within MailerLite so you can provide them to your domain company.

If you have not authenticated your domain, you should make it a priority. Spammers will often attempt an “email spoof”, where they take control of your domain to send unauthorized emails. This would damage your domain reputation and hurt email deliverability rates.

The good news is that you only need to authenticate your domain once, and you are all set to send emails from your address with a verified domain.

If you have any trouble, here are several more resources to help you authenticate your domain using MailerLite.

Email service providers (ESP) like MailerLite use shared IP addresses so that email marketers who aren’t sending enough emails to maintain a good sender reputation on their own can still maintain good deliverability by sending from an IP address with a good reputation.

If you’re sending upwards of 50,000 emails per week, you may benefit from a dedicated IP address. This is an IP address that only your account sends from, the benefit of which is that nobody can affect your IP’s reputation except you. 

Keep in mind that it takes a lot of volume to warm up and maintain a good reputation on a new IP address. If your email sendings decrease or stall, your IP reputation will decrease and you may end up on an IP blocklist.

We know you’re not a spammer. You know you’re not a spammer. But unfortunately, there are spam filters that are not sophisticated enough to distinguish quality emails from spammers.

Email providers like Gmail and Outlook do everything in their power to protect their users from spam. One way they try to detect spam is to scan every email for spam trigger words, phrases, and styles that are commonly used by spammers.

Unfortunately, these spam filters will also flag your perfectly legit email just because you unknowingly used an email practice associated with spam.

By avoiding these red flags, you will have a much easier time reaching the inbox.

What are the spam filters looking for?

Are you using links in your email?

Double check that you only link to quality sites, especially if you work with affiliates. Also, spammers like to hide their devious links by using shortened URLs like links, so avoid those when possible.

Are you using ‘spammy’ words in your subject line and content?

Spam filters look for certain words and phrases that are too ‘salesy’. You can use a content checking tool that will automatically check your content and flag spam-like words and phrases., Once you replace the trigger with safe alternatives, you’ll send with confidence.

Are you using a lot of exclamation points or ALL CAPS?

It’s okay to get excited about your email by using one exclamation point, but spammers love to use several exclamation points or ALL CAPS to entice people. Spam filters are looking for this type of excessive formatting.

Are you writing in red font?

Different colored fonts are a great way to emphasize a word or phrase visually, but unfortunately, spammers have made the color ‘red’ a red flag. Instead of red, try using another color that matches your brand.

Are you using images correctly?

Spam filters see images as empty spaces, so never create your newsletter as one big image. When you use images, fill the empty spaces with ALT text and a short image description.

Are you personalizing content?

The difference between you and a spammer is that you know your subscriber. You can show spam filters that you know your subscribers by adding personalization tags.

Deliverability testing is a key component in any email marketing strategy. You’ve already taken the time to authenticate your domain and optimize your newsletter content. So take the extra measure of testing your emails to ensure that they’re optimized.

There is a lot to watch out for when sending email campaigns. Luckily, there are email deliverability testing tools that can check your emails for you. 

How can email testing tools help?

Spam filter tests

Email testing tools can test your emails against common spam filters such as SpamAssassin. Spam filter tests give you an idea of how a typical spam filter will review your email's content.

Content checks

While you may have already proofread your newsletter to the nth degree, you might not notice common phrases in your content that will be picked up by a spam filter, email testing tools will. You can then remove any flagged words or phrases from your newsletter before sending.

Inbox placement

Email testing can give you a sneak peek into where your marketing emails land. If you find that your email is landing in the spam folder, you’ll have the chance to implement email deliverability best practices before sending the campaign to your subscribers.

Links and images validation

Email testing tools can review each link and image within your campaign’s content in order to find broken paths, missing properties, or profanity within the filename. All of which would otherwise trigger a spam filter.

Up until now, we’ve focused on trying to appease the email providers, but at the end of the day, optimal deliverability is all about subscriber satisfaction. Now it’s time to focus on crafting emails people care about.

The protective measures that email providers implement are meant to protect the end-user (the person who receives the email). The happier your subscribers, the more email providers will love you.

happy email subscriber - emails are landing in his inbox

How do email providers know that you are making your subscribers happy?

Email providers track how your subscribers interact with your newsletters to decide if you are making them happy. These interactions are both positive and negative and depend on your subscribers’ actions.

Positive actions from your subscribers include:

  • Opening your newsletters

  • Moving newsletters from and to different folders or sections, for example, from Promotions to Primary tab

  • Adding your (sender) email address to their address book

  • Replying to your newsletters

  • Forwarding your newsletters

  • Saving newsletters from the spam folder, by marking them as “not spam”

Use segmentation to encourage positive actions

Create segments to differentiate your subscribers based on their activity and other information that you have about them. You can then create more targeted campaigns that yield more positive actions. Learn more about segmentation here.

Work on improving these metrics by encouraging your readers to reply or share some of your emails, save your sender address in their address book or move your newsletter out of the spam folder if it happens to be there.  

Negative actions from your subscribers include:

  • Not opening your newsletters at all

  • Deleting your newsletters before opening

  • Marking your newsletters as spam

While there are only a few negative metrics, they do outweigh the positive ones. So how do you prevent these negative actions?

Follow through on your original promise. Keep delivering the value you offered your subscribers at the get-go.

Get your timing right

Inboxes are always crowded. So you want to find the right time to land in your subscribers' inboxes to maximize the open rates. Learn how to get your timing right in this article on the best time to send emails.

Whether you like it or not, your contact list contains invalid emails that must be removed before your bounce rate gets too high.

A bounced email is an email that cannot be delivered and is returned to the sender. There are two types of bounces: soft bounces and hard bounces.

email deliverability hard soft bounce example

Bounces, especially hard bounces caused by invalid emails, damage your sender reputation and the deliverability of future newsletters. If your bounce rate creeps above 5%, it means that you have a lot of non-existing email addresses.

To clean your list of invalid emails, you can use a validation tool to verify every address on your list. You can also add some steps to your sign-up process to prevent future invalid emails from infiltrating your list.

Let's go over your options to help you clean your subscriber list and keep it healthy.

Identify and remove invalid emails

The easiest way to identify and remove invalid emails is to use email validation tools.

You can upload your list and the validation technology will detect invalid email addresses for you to remove. Doing so can reduce your bounce rate by 98% and help your newsletters get delivered to the inbox.

Validate your list when migrating from another email service

Moving from one platform to another is a great opportunity to validate your list. Run your subscribers through a validation tool before sending your first newsletter.

Validation tools can also categorize your email list to identify emails that might be spam traps (they can’t identify everyone), emails that contain typos and emails with full mailboxes.

Armed with these insights, you can clean and organize your subscriber list to prevent bounces.

Prevent future invalid emails

For starters, the worst thing you can do is purchase a list. You are almost guaranteed to add spam traps and ruin your healthy subscriber list. It’s not worth it!

Beyond not buying lists, the best way to start avoiding invalid email addresses is by adding double opt-in and/or reCAPTCHA features to your sign-up process.

With double opt-in, your new subscribers receive a confirmation email after they sign up. The new address is not placed on your list until a real person confirms the subscription. This serves as a protective shield from email addresses that were submitted with typos, from bot attacks that submit fake email addresses and from adding spam traps.

double opt in example for better email deliverability

You can implement double opt-in in MailerLite on any of the sign-up forms and with API integrations.


The second layer of defense against invalid emails is reCAPTCHA, which is the small checkbox at the end of a sign-up form that usually states, “I am not a robot.”  The primary purpose of reCAPTCHA is to protect websites from spam and abuse by making it hard for bots to sign up on your form. 

recaptcha example to improve email list quality

If you use MailerLite, you can add reCaptcha by checking the box in your settings. A more detailed description of adding reCaptcha to your sign-up forms can be found here.

Email providers like Gmail, Outlook, and Yahoo monitor how your subscribers interact with your emails. Lower engagement results in poorer deliverability. Inactive subscribers are people who signed up at one point, but no longer open your emails. They don’t click on any links. They don’t show any signs of life.

When you keep sending emails to people who are not opening your newsletters, the spam filters will eventually move your newsletter to the spam folder.

If a subscriber has not shown signs of life for six months, you should remove them from your active list.

You don’t have to completely remove those inactive subscribers from your database. You have the option to create a segment of inactive subscribers and set up a re-engagement campaign to win them back.

If they still don’t open your newsletters, you should consider unsubscribing them. It’s hard to say goodbye, but it will ensure that your active subscribers receive your newsletters.

Remove old subscribers

If you’re moving your subscriber list to a new email marketing platform, remove old subscribers that you haven't contacted in a while from your list to reduce the risk of spam complaints. The longer you go without contacting a subscriber, the less likely they are to remember you.

Make it easy to unsubscribe

Did you know that when people unsubscribe from your newsletters, it does not negatively affect your deliverability? For uninterested subscribers, unsubscribing is a good thing.

Many people mark emails as spam just because they can’t find the unsubscribe link. Spam complaints are NOT good for email deliverability. Some email providers will start blocking email senders with only 2-3 spam reports per one thousand emails.

Make sure your emails always have a visible unsubscribe link in the footer section.

Think of your unsubscribe link as an automated list-cleaning tool. You can use your unsubscribe survey to learn why your readers leave, but if people no longer want to hear from you, it’s best to let them go.

Read more on how to customize your Unsubscribe Page

Quality always outperforms quantity

Improved email deliverability starts with safe newsletter content and a healthy subscriber list. When your emails are clean and sent from authenticated sender addresses, you’ve done all you can to maximize deliverability.

Resist the temptation to send to a huge list that’s not been verified. Respect the inbox and you will be rewarded!

Have you noticed any changes in your engagement metrics after using these best practices? Share your experiences below!

Gabija Trimbel
Gabija Trimbel
I’m Gabija, Deliverability Manager at MailerLite. I spend my days making sure that your emails are delivered. Email deliverability is a complex and fascinating aspect of email marketing that constantly keeps me on my toes. To be honest, sometimes I wish I had an easier job like a rocket scientist or ninja master.