email deliverability

Improve Email Deliverability with These 16 Definitive Tips

Email marketing is a very promising and effective way to sell goods and services. However, you can send a lot of emails and never get results if your emails aren’t delivered to recipients’ inboxes. Or, on a less drastic scale, if your email delivery is less than ideal, you will reduce the effectiveness of your campaign.

Practically speaking, emails are useless unless your audience actually receives them. In this case, a failure to receive the email can include your emails being relegated to the spam folder, in addition to those that bounce because the address is wrong.

But, what is the solution? Besides best practices for email composition, you want to ensure your email deliverability is optimal.

What is Email Deliverability?

In a nutshell, email deliverability is the ability of your marketing emails to arrive in your recipient’s email boxes. You would consider emails delivered if they don’t get blocked or returned and end up anywhere besides the recipient’s spam folders.

There are several reasons why your email might not get delivered. One of the causes of non-delivery is that an ISP or email provider can decide that your promotional emails are actually spam. And, of course, having a lot of your emails marked spam by recipients can encourage this finding. Another reason is that your email list is out of date. To minimize this, you want to consistently cull your list so that the same addresses aren’t constantly returning your emails.

Why Does Email Deliverability Matter to Your Business?


Email marketing has the highest return on investment (ROI) compared to other marketing channels. For every dollar spent on email marketing, you get an ROI of $40. Of course, as a business, you should be doing email marketing. Not only is it highly effective, but it’s a very inexpensive marketing method. In other words, email marketing is accessible to almost any business.

Of course, the effectiveness of email marketing means that every email that bounces or lands in the spam folder is a lost opportunity. Similarly, the fewer emails that land in inboxes, the less ROI you receive because each email sent costs money. Therefore, a high level of email deliverability also improves overall ROI and saves money.

How Does Email Deliverability Work?

It works by getting your content into the boxes of your audience. To accomplish high email deliverability, you need to maximize each step in the process. You also need to maximize each of the delivery factors, which we’ll talk about in the next section. For now, let’s focus on the email delivery process.

4 Components of an Email Delivery Process

For most of us, sending an email comes automatically — simply click compose in your email client, type or paste what you want to say, add recipients and subject lines, and click send. For commercial emails, it’s a little more complicated. Not only do you need to create content that will appeal to more than one person, but understanding the overall process will help you master what’s needed to maximize email deliverability.

1. Email Sender 

First, all emails originate with an email sender. Essentially, this is any business sending out emails as a part of an email marketing campaign. Non-bulk or non-marketing emails, especially those that are sent individually, are not the ones that we’re discussing here. That’s because deliverability is primarily an issue when you send many emails at once.

2. Email Service Provider

Email Service Provider

Email service providers, or ESPs, are third parties that help you with your email marketing and automation. Typically, businesses will use these services to send and receive the emails themselves. Examples include Gmail, Yahoo, and Outlook. Your ESP will also let you send out one-off emails.

For recipients, the ESP shows up as the “@” portion of your email address.

3. Gateways

Gateways are companies (platforms) that help you send emails. There are several types of gateways, many of which will also help determine your email delivery. In other words, they can be more than just a way to send and receive emails. Strictly speaking, your ESP is a gateway as well. Other gateways include your internet service provider (ISP), anti-spam systems, blacklisting organizations, and the recipients’ spam filters.

In order to have your email delivered, you need to pass through each of these gateways. Many of them can “veto” email delivery, classify them as promotional, or relegate emails to the spam folder. Therefore, it’s important that these companies understand that your company is reputable.

4. Recipients

Finally, your subscriber or customer is the recipient of each email. Overall, the goal of deliverability is for all of your intended recipients to receive the email, with the exception of newly disconnected addresses. That’s because if an address has recently been disconnected, you haven’t had time to take it off your list. This interval should be as short as possible.

The 6 Main Factors that Impact Email Deliverability

Now that we understand the basics of getting your emails delivered let’s talk about the different factors that help get yours into that inbox. This way, it’ll be easier to understand how we can boost email deliverability for maximum ROI.

1. Sender’s Reputation

This is assessed by your ISP. They perform a reputation check and score you on a scale of 0-100 to figure out if you are a legitimate business. If your score is low, your email is unlikely to make it to your recipient’s inbox. Instead, your emails will likely end up in everybody’s spam folders.

But what goes into a sender’s reputation? One of the biggest drivers of a positive or negative reputation is the extent to which your emails are actually delivered. This means that email addresses that bounce should be removed right away. Likewise, higher open rates are helpful to your reputation, while a large number of spam reports are harmful. We will talk about best practices in the next section.

2. Engagement

Engagement is how the recipients respond to your email – whether they open it, ignore it, spam it or unsubscribe. ISPs monitor the engagement.  For this reason, positive engagement helps your emails get delivered, while negative engagement makes them more difficult. One reason that these metrics are so useful is that they don’t require an email provider to “read” every email in order to police spam. Instead, they use subscriber behavior to judge whether or not a sender is trustworthy.

3. Spam Filters

This is the software that’s used by ISPs to scan incoming messages. It can either mark your message as spam or allow it through. A rate of 0.02 percent spam flagging is enough to cause deliverability issues. Therefore, even if your emails are top-notch, only a few customers marking your email as spam can cause significant problems.

4. Email Bounces

When you send an email to an invalid email address, the email bounces. If your bounce rate is high, it will directly impact your sender’s reputation and future email deliverability. Emails can either soft bounce or hard bounce. A soft bounce happens when too much email is going to the system at any given time, and the email software or ISP wants to reduce traffic temporarily.

A hard bounce happens when an email was no longer being used and has been disconnected. Hard bounces should result in that address being removed from your list immediately. This is one of the best ways to manage your bounce rate.

5. Email Content

Email Content

Emails need to contain content that is relevant to your intended recipient. This includes the subject line, body text and supporting images, and links. Certain words may also trigger spam alerts and send your email straight to the spam folder. Some easy examples include all caps, funny fonts, scammy words, and others that appear to solicit information from the recipient.

However, there’s more to having good email content than just words. Email codes like <embed> tags or JavaScript that are malicious can also impact your deliverability. Also, if the URLs in your email link to sites with a poor reputation, your deliverability will take a direct hit. In other words, ISPs try to keep consumer inboxes safe from scams and malicious content. Fortunately, unless your company’s computer system gets infiltrated by a virus, this shouldn’t be a problem for legitimate businesses.

Further Reading: How to Create the Perfect Content for Your Email Marketing

6. Blacklists

Emails sent from blacklisted servers or domains will never make it to the inbox. Simply put, blacklists are real-time databases kept by ISPs and email providers. These lists identify domains and servers that send emails flagged by spam filters.

It’s relatively easy to get placed on a blacklist. For instance, if too many people report your emails as spam, it can land you on a blacklist. The same thing goes with sending too many emails too fast or buying pre-made email address lists. Again, the careful use of best practices helps companies avoid blacklists when at all possible.

16 Email Deliverability Best Practices

As you can see, there are quite a few ways to develop problems with email deliverability. After all, ISPs and ESPs try to keep harmful and time-wasting emails out of people’s inboxes. And, of course, deliverability issues can seriously undermine the effectiveness of your email campaign. Luckily, by following these email deliverability best practices, you can maximize the effectiveness of your efforts.

1. Keep Your Email Content Precise 

First, make sure that your email is concise. Wordy emails can trigger spam filters when they come from email addresses that send a lot of emails. Think about it a minute — how many of the emails in your spam folder drone on and on? This is especially common with scam emails and the ones which are peddling questionable consumer products.

It also is a good practice to keep your message precise for other reasons. Customers get a lot of commercial emails every day, and most of them will simply scan each email to see if they’re interested in the product, service, or special being promoted. Of course, that’s if the email even gets opened. A great way to see people unsubscribe in large numbers is to waste their time. You can always direct people to landing pages on your website for extra details.

Further Reading: Looking for Email Marketing Templates? Here are My Top 15 Recommendations

2. Get Yourself Verified by a Third Party

This process is called sender accreditation. Verifying your identity with a third party puts you in a whitelist and helps you avoid spam filters, thus increasing deliverability. Make sure you abide by TLS, SPF, DKIM, and DMARC authentication methods. Best of all, it’s usually an easy process.

3. Check the Reputation of Your IP

If your IP address has a bad reputation, your emails will hardly make it to your recipient’s inbox. A quick way to check is by going to Remember, the higher the score, the more your emails will get delivered. If you have a lower score, you’ll want to find out why your score is low. Your ESP or corporate IT department can help you with this process.

4. Set Up MX Records 

An MX record is a set of instructions for how each of your emails should be sent to recipients. For instance, you might have your emails sent primarily through one server, with a second one serving as a standby. Or for brands with large email lists, the MX record may specify that a certain percentage of emails be sent through each server. This practice helps avoid many of the issues with server overload that hurt email deliverability.

Some ISPs automatically block emails from senders that don’t have a valid MX record. There are a couple of reasons for this. First, the process of setting an MX record helps indicate that the sender is a legitimate business rather than a spammer who doesn’t care about quality or server overloads. Secondly, the practice helps to protect the ISP’s servers. Otherwise, a server overload might harm the user experience for everyone using the ISP.

5. Make Unsubscribing Easy

Not providing the option to unsubscribe is illegal in some countries, including the United States. The unsubscribe option should be clearly visible, preferably in the footer of the email copy. And once they unsubscribe, make sure you remove them from your list.

Managing unsubscribe lists properly is an important way of maintaining the hygiene of your email list. Frequently, an unsubscribe request denial leads to future emails being marked as spam, which in turn hurts your sender’s reputation. If you are using email marketing software, it will take care of this automatically. 

6. Send Emails from a Real Person 

Emails from a real person have a higher open rate. Naturally, you don’t have to have the individual send each email manually. Instead, sending from a real person is much like those pieces of personalized paper mailings that are signed by a particular member of staff. In this case, you would use that person’s email address as the sender and include their name in the signature line. People love it when they feel like they’re more than just a number or potential paycheck.

Again, if you use email software, then it’s easy to set this up. Typically, it will be a matter of checking a few boxes. Also, if you have just one email address for the whole company, associate it with an important employee like the president.

7. Personalize Your Emails

Similarly, you should always personalize commercial emails. For example, include your recipient’s name in the ‘to’ field, and not just the address. This will let the spam filters know that the email was actually addressed to someone you know, like your subscriber or customer. 

If you’ve ever signed up for an email list, especially in the B2B space, then you know how this works. Usually, you need to give a name when you subscribe instead of merely putting your email address down and clicking send. Plus, the personalized touch helps build a relationship between you and the email recipient.

Further Reading: 12 Ways How to Improve Your Email Open Rate

8. Separate Transactional Emails from Marketing Emails

Separate Transactional Emails from Marketing Emails

Separate your transactional emails from marketing emails. One reason to do this is to transactional emails and marketing campaigns being sent together increase the volume of total emails sent from a single email address. You don’t want that to happen because the combined volume will count against your sender reputation score. Then, if you get blacklisted, it’ll make sending transactional emails more difficult. That’s in addition to the trouble it will cause with marketing campaigns.

Use a separate IP and subdomain to ensure deliverability. In other words, you want it to be clear which emails are being sent from what address. As a bonus, you might find that transactional emails will go in a customer’s “main” email folder (like Gmail), and the others will be filed under promotional emails. This can be very convenient for the customer because it’s easier for them to track a package or find a transactional email to save relevant financial records.

9. Ask Your Subscribers to Whitelist Your Email

asking subscribers for a place on the whitelist is extremely effective for boosting email deliverability. Whitelisting means that your email domain is trusted by the consumer, which bypasses their spam filter. The easiest way for people to whitelist your email is by adding it to their contact list or address book. You can easily request this in any of your campaigns, though it’s likely to be very effective when added to your onboarding email.

10. Send HTML and Plain Text Versions 

One size doesn’t necessarily fit all. In other words, an HTML email isn’t appropriate for everyone, even though they are far more popular these days. In addition, plaintext emails work well for people who don’t have access to high-speed Internet, or who might be on a metered connection due to travel.

Besides convenience to customers, sending two versions of your email helps build credibility and legitimacy with the ISPs. One reason for this is that spammers generally focus on email quantity, not quality. This emphasis spills over into not sending two versions of the same email. Also, make sure your HTML version is properly coded to avoid triggering a spam filter. Generally speaking, poor-quality emails are a major red flag for spam.

11. Use Double Opt-in instead of Single Opt-in

Single opt-in is a single-step process where the users just have to enter their email and are added to the list. With double opt-in, a confirmation email is sent to the user, which they have to open and click before they are added to the list. Double opt-in is a best practice that helps ensure that only interested parties are added to your email list. In addition, it helps you avoid some of the regulatory pitfalls of email marketing.

12. Segment Your Email List

Segment your subscribers into categories based on their response rate. For example – New for new subscribers, Passive for old subs who haven’t opened your mail for more than 30 days, and inactive for subscribers who haven’t opened your emails in over 180 days. You can also segment users based on the buyer’s journey and send personalized emails for a higher open rate.

Members of each segment should receive a different type of email, such as a re-engagement email or a special offer aimed at earning their business. For more active subscribers, you might tailor a message to their stage in the buyer journey.

Further Reading: How to Grow Your Email List: 13 Best Practices to Follow

13. Weed Out Inactive Subscribers

Inactive subscribers impact your email deliverability so make sure you remove users that are not responding to your emails in any way. It’s okay if they’re opening the email, at least on occasion. But, over time, your inactive subscribers will reduce your engagement rate while also costing you the money required to send them emails.

Remember, ISPs and ESPs pay attention to how often people open, read, and click through your emails. This is a good indicator of how well you pay attention to your customers. In addition, spammers tend to have very low response rates, so being in that category provides a major red flag.

14. Check the Quality of Your Email List

You can use tools like Clearout or DeBounce to check if your list has only valid email addresses. Typically, you can upload your CSV file into the tool, and it will automatically analyze your addresses. You should also monitor emails that receive a hard bounce. These usually come with a message from the email subsystem indicating that the message was undeliverable. With an ESP, those addresses are automatically removed. But it never hurts to check for other low-quality addresses too.

Further Reading: 7 Best Ways to Build an Email List (From Scratch)

15. Maintain Image Text Ratio

Maintain Image Text Ratio

This is not a super crucial factor to trigger spam filters, but it’s a good practice to maintain a ratio of 60:40 of text and images in your email content. In this case, you want an aesthetically pleasing yet easy-to-read email. You don’t want to overwhelm your subscribers with flashy visual images that overload the sciences. Likewise, a big text box is unlikely to catch their attention. About the only exception to this second rule is a newsletter, and even then, you probably want to break up a bit.

16. Check Your Spelling 

Spelling mistakes in your email are not only unprofessional, but they can also trigger spam filters. Once again, part of the issue is email quality. Spammers send poor-quality emails in bulk rather than focusing on quality over quantity. Also, it’s helpful to think about the sloppy spam emails you get every so often. The worst offenders are usually full of spelling and grammar errors, and they often appear to be written by someone whose English is poor.

Don’t be that email sender.

What NOT to Do for Higher Email Deliverability

Finally, let’s look at a few practices you should avoid for the best email deliverability results. Many of these are counterpoints to the best practices discussed above.

  • Don’t send emails from your free personal email. Not only is it unprofessional, but it’s a good way to get your personal email blacklisted, banned, or even closed. Personal emails are not intended for sending bulk commercial messages.
  • Don’t use spam trigger words like losing weight, help, urgent, free, 100%, etc. in your email subject line. Instead, when these words are actually necessary, put them in the body of the text. However, you’ll find that unless your legitimate business is related to those terms, you’ll rarely need them.
  • Don’t use URL shorteners. For some reason, URL shortener use can serve as a red flag. However, the body of your email has plenty of space for a full URL, and these provide transparency about where you’re sending your subscribers.
  • Don’t buy email lists or scrape emails from the web. There are a couple of reasons for this. First, in some jurisdictions, this practice may be illegal, such as with the CAN-SPAM Act. Second, email lists can be very low quality. Not only do they frequently include a lot of invalid emails, but they’ll also include some spam traps. A spam trap is a fake email address maintained by keepers of blacklists. In other words, scraping and purchasing lists are a great way to get blacklisted.
  • Don’t use Caps in your subject line or the email body copy. Once again, it’s unprofessional and sloppy. Acronyms are okay to use as appropriate, but besides this, you should remember that CAN be construed as shouting. It’s another mistake that spammers frequently make.
  • Don’t embed forms or include attachments unnecessarily. This can cause your emails to consume a lot of data. Use attachments when you need to, but this is usually the case with transactional emails. You don’t want to look like a data harvester, either.
  • Don’t email users that have bounced constantly. Not only does the email address likely not exist anymore, but high bounce rates reduce your quality scores with ISPs and ESPs. Both of these issues can reduce your email deliverability.

How to Test Email Deliverability?

Finally, it’s always important to gauge your brand’s email deliverability. By far, the easiest way is to use tools to run email deliverability tests. Providers include Senderscore, Glock apps, SenderPost, and Mailtrap. Each of these tools has different features, but they’ll all tell you how well your emails are performing. Then, you can figure out how to improve your email delivery and boost the ROI of your campaigns.

The Final Word on Email Deliverability

Whether you have a large business or a small one, you should be doing some level of email marketing. However, even the best emails are only as good as your ability to have them delivered to recipients. That’s why we spend so much time and effort working on email deliverability. Whether it’s carefully crafting your emails, using optional features like MX records and third-party verification, or building your email list the right way, you will find the effort worthwhile.

Hero Photo by Brett Jordan on Unsplash

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Neal Schaffer
Neal Schaffer

Neal Schaffer is a leading authority on helping businesses through their digital transformation of sales and marketing through consulting, training, and helping enterprises large and small develop and execute on social media marketing strategy, influencer marketing, and social selling initiatives. President of the social media agency PDCA Social, Neal also teaches digital media to executives at Rutgers University, the Irish Management Institute (Ireland), and the University of Jyvaskyla (Finland). Fluent in Japanese and Mandarin Chinese, Neal is a popular keynote speaker and has been invited to speak about digital media on four continents in a dozen countries. He is also the author of 3 books on social media, including Maximize Your Social (Wiley), and in late 2019 will publish his 4th book, The Business of Influence (HarperCollins), on educating the market on the why and how every business should leverage the potential of influencer marketing. Neal resides in Irvine, California but also frequently travels to Japan.

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