How to Improve the Deliverability of Email Marketing

Melanie Balke
June 29, 2023

Here’s some food for thought: If you’re sending out emails and nobody is there to read them, are you really marketing?

It’s that old “if a tree falls in a forest” problem, but this question has a very real financial impact!

Your email marketing is expensive. It’s a time-consuming labor of love, one of the big driving forces behind your brand’s success. So, naturally, you want people to see those messages!

An email’s ability to land in an inbox — as opposed to the spam folder or some other tab — is known as email deliverability, and it’s the topic of today’s blog post.

What Is Email Deliverability?

An 1873 patent for a stamp-affixing machine. Overlaid text reads, "The Basics: What Is Email Deliverability?"

The definition is simple.

Email deliverability is a brand’s ability to reach consumers. It’s a proven, empirical measurement that can guide your email marketing strategy. However, the actual workings are rather complex!

Many factors determine your email deliverability, including:

  • Authentication
  • Bounces
  • Sender score (also known as “sender reputation”)
  • Subject lines and email content

You’ll find plenty of sources that focus on one or two of these topics. They may even tell you ways to improve your deliverability! But… they’re hiding something: You need to work on all these factors to nail your email deliverability!

So, with that in mind, let’s go down the list…

What Is Authentication?

An abstract cameo-type pattern. "Authentication: Protect Yourself."

Aside from being the first alphabetically, authentication should be one of your first practical concerns! You can’t improve your email deliverability if your address is unverified. Similarly, you can’t expect internet service providers to give your anonymous account free access to their valued clientele.

Think of it as your email account’s driver’s license, a formal way to prove you are who you claim to be. Whenever you send an email, the recipient’s inbox checks your authentication before sorting your content. Using the same analogy, this would be like carding you at a bar.

Why Do We Need Email Authentication?

A wavy pattern. "The Purpose: Why does authentication impact your overall email deliverability?"

“But,” you may be saying, “why do I need to verify my business’ identity!?”

Well, let’s take the driver’s license comparison a bit further. Like a legal ID, your authentication protects you and the people around you! It protects you from impersonators and makes it harder for people to smear your carefully cultivated reputation.

See, emails use old tech. Their framework, known as standard mail transfer protocol (SMTP), has no way to flag a sender’s true identity. This was a non-issue in the early days, but the 1990s changed everything. With massive access came massive scams, and bad actors began spoofing well-known email addresses.

Fortunately, the solution arrived quickly. Email authentication was — and still is — meant to combat scammers. Yes, it may seem like an inconvenient nuisance, but it’s a must-have for any email marketing program.

Authorizing With SPF and DKIM

A chart displaying a television schedule from 1954. Overlaid text reads, "The Essentials: The ins and outs of DKIM and SPF authentication."

The two most common methods of email authentication are sender policy framework (SPF) and DomainKeys identified mail (DKIM). These standardized approaches work on a near-universal basis, and proper registration through these outlets goes a long way to avoiding the spam folder!

These approaches are often grouped together, but SPF and DKIM are not the same thing.

Perhaps the most established method is SPF. The technique was proposed in the early 2000s and has seen consistent, reliable use since its inception. Unlike its sibling, DKIM, SPF relies on a pre-determined list of verified domains.

As an example, let’s say you configure your SPF settings to allow emails from your own website (let’s go with “”), Gmail, and Hotmail. With SPF, any emails from these domains will be considered authentic. However, if someone were to spoof your domain from a Yahoo Mail server, that message would get flagged as spam.

Conversely, DKIM authentication uses built-in digital signatures to verify your content. In reality, these “signatures” are more like house keys. They’re unique codes that can be passed to trusted senders, who subsequently embed that information in each campaign.

Both SPF and DKIM can be thought of as your first line of defense. They’re reliable and well-established, but they can still fail. And, when they fail, you’ll need a failsafe, such as…

Domain-Based Message Authentication, Reporting, and Conformance (DMARC)

An old computer. "DMARC: An Essential Deliverability Tool for Email Marketers."

This mouthful of tech is established enough to warrant official recommendations from the Federal Trade Commission, so it’s well worth the extra work. But what is DMARC?

At its core, DMARC is a splinter of both DKIM and SPF. However, unlike its predecessors, DMARC offers businesses the ability to customize email authentication. More precisely, users can choose which system a recipient’s inbox providers should use (SPF, DKIM, or both) and what happens when a server encounters an error. DMARC can also verify and correct an email’s “from” line to match customer expectations.

Ultimately, the email marketing tools DMARC offers are indispensable. Its highly variable configuration is its main selling point, and domain owners can use these variables to slowly move older or unverified email addresses to proper DKIM and SPF setups.

Bounces and Failed Deliveries

A bouncing tennis ball. "The Metrics: Understanding Bounces."

Now that you’ve verified your email addresses, it’s time to look at your metrics. I want you to pay particular attention to your bounce rates. These percentages tell you how many people failed to receive your email marketing, and they impact your overall reputation (more on that in a minute).

The Hard Bounce

Assorted steel parts. "Hard Bounces: Serious and permanent delivery failures."

Of the two bounce types, the hard bounce is the scariest. These are permanent delivery failures, and they severely impact your ability to run successful email campaigns!

There are a few different ways to get a hard bounce, but the three most common are as follows:

  • Being blocked by the recipient
  • Being flagged as spam
  • Emailing a non-existent address

Aside from being a waste of funds and time, hard bounces lower your IP reputation (again, more on that soon!). Moreover, having a high hard bounce rate indicates that you have a big problem. The issue may be as simple as failing to remove inactive subscribers, but there are plenty of serious causes for hard bounces. For example, an internet service provider may have added your domain to a blacklist!

The Soft Bounce

Molten metal in a forge. "Soft Bounces: Temporary delivery failures."

You can also encounter a soft bounce, which is a temporary delivery failure. Now, don’t get me wrong… a soft bounce is still a failed delivery. That email probably won’t reach subscribers’ inboxes after you fix the problem, but these aren’t nearly as bad as hard bounces.

Common causes of soft bounces include:

  • Failed authentication checks
  • Full inboxes
  • Inactive email addresses
  • Server outages (from email service providers, internet service providers, or both!)

Nonetheless, both hard and soft bounces can impact something known as…

Sender Reputation

Blurred text with an overlaid header. "The Numbers: Know Your Sender Reputation."

This is where you really need to pay attention.

Your sender reputation (also known as a sender score) isn’t easy to check, but it’s one of the biggest players in the email deliverability game. This invisible score tells email service providers how often you should be penalized for innocuous spam trigger words and whether or not you’ll get tossed into the dreaded spam folder. In other words: If you want email marketing success, you need a good sender reputation.

What Influences Your Email Sender Reputation?

Wavy parallel lines. "Influences: Various factors impact your sender reputation, including spam reports!"

Like everything else in email marketing, your sender score is the culmination of many things. It’s an amalgamation of your past, present, and future. Or, to put it less cryptically, it’s a numeric rating based on factors such as:

  • Bounce rates
  • Email authentication protocols
  • Having a dedicated IP address
  • Legal compliance
  • List building techniques (e.g., single opt-in versus double opt-in)
  • Proper list hygiene
  • Spam complaints

Avoid Purchased Email Lists

Streaks of light. "Don't Buy Lists! Purchase email lists are full of spam traps."

So, how can you improve your sender reputation?

For starters, never use purchased email lists. In fact, don’t purchase them in the first place! Moral implications aside, these lists rarely lead to qualified leads. At best, you’ll annoy people and generate a spam complaint or two. Alternatively, you could experience the worst outcome and end up in legal trouble!

Notably, many purchased email lists contain fake email addresses and spam traps. Both of these can negatively impact your sender’s reputation.

The leads you buy are never worth the risk, so leave those so-called “miracle marketing lists” alone! The best brands are built around a core of organic enthusiasts. These customers are loyal supporters, not randomized email addresses. Cater to them, and you’re bound to see growth!

(Oh! And don’t trust anyone who says you can “get away” with it. You will get caught and do not want to face those fines!)

Don’t Avoid the Law

Abstract lines. "Know the Law: Know What Legal Codes Your Marketing Must Follow."

Speaking of legal trouble…

Never try to evade the law.

Know your laws! In North America, you’ll want to study Canada’s digital marketing legislation in addition to the United States’ CAN-SPAM Act and CCPA. Working “across the pond?” You’ll need to brush up on the European Union’s General Data Protection Regulation (GDPR).

In a general sense, every email should include the following information:

  • Customer service contact information
  • (For double opt-in emails) a confirmation link
  • A physical address (or valid legal equivalent)
  • Relevant content regarding legal disclaimers
  • A valid phone number
  • A working unsubscribe link

Note that many email marketing platforms provide these elements by default; you’ll usually find them in the footer. However, a good email marketer can place these elements wherever they want, provided that they elements are clearly visible.

Failing to abide by these guidelines can put you on the wrong side of the law and your email service providers. In fact, almost every email marketing platform retains the right to refuse service to non-compliant businesses.

Polish Your Subject Lines (and Content!)

Layers of written words. "Content: Make Emails Worth Reading."

This next section comes with a bit of a caveat. If you’re just starting your email marketing program (or you have a poor sender reputation), you’ll want to pay close attention to your content. However, “broken-in” email addresses will have fewer deliverability problems.

Summarily: Everyone will have different results if they measure how this bit affects email deliverability.

Nonetheless, I’d be doing my readers a disservice if I failed to mention how content impacts overall deliverability.

Know What Goes to the Spam Folder

Letters painted on canvas. "Avoid Triggers: Some words are more likely to get flagged as spam."

All email service providers have protocols in place to protect users.

Some words — collectively known as “trigger words” — are more likely to trip spam filters and negatively impact email deliverability. Again, the strength of this effect depends on the email sender’s reputation (and a few other factors), so established accounts shouldn’t worry too much about this.

Generally, you want to avoid things that make a message appear illegitimate, such as:

  • “Clickbait” subject lines
  • Excessive emoji use
  • Excessive punctuation
  • Non-standard characters
  • Poor grammar

These traits are likely to trigger spam filters. They’re also seen as a nuisance, and they’re unlikely to be read even if they make it to subscribers’ inboxes. In particularly egregious cases of abuse, many email clients will refuse a message altogether! That’s right; the email client will delete your email campaign before it even reaches the spam folder.

Make That Subject Line Shine

Old newspapers with overlaid text. "Subject Lines: Grab attention by polishing your subject line."

Here’s another tip: Master the art of the subject line. It is, after all, your first impression. It’s what makes or breaks email marketing campaigns. A good subject line can recapture inactive subscribers; a bad one scares off new customers.

Let’s forget about email deliverability for a second!

Just think about subject lines.

How can you make your marketing emails stand out? What sort of words appeal to your audience?

Take those ideas and apply them to every email campaign.

Now think about email marketing deliverability.

Much of what I said in the last section still applies. You want to avoid anything that makes your content seem like anything but legitimate emails. Avoid those copy-and-paste Twitter “fonts.” Keep punctuation to a minimum. More importantly: Think about how your email message looks in subscribers’ inboxes.

Organize Your Content

Lines of code. "Content: Organize your content to make information accessible."

Finally, take a look at your email marketing program, paying particular attention to your body copy. Ask yourself some questions…

  • Does it flow?
  • Does this content create excitement?
  • Have I implemented a proper plain-text version of this content?
  • Is my content engaging?
  • Is the content accessible?
  • Is this relevant content?

If you can confidently answer “yes” to all of the questions, then you’re in great shape!

But don’t get too comfortable.

You still want to ensure every message can pass through a spam filter. Again, think about those trigger words! I find that it helps to browse through some of your filtered mail to see what spam messages have in common. You can also find plenty of tips from email marketers online!

Boost Your Email Marketing Campaign Today!

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That was a lot of information, right?

If you’re feeling a little overwhelmed right now, that’s okay! It takes a lot of work to maintain high email deliverability, and internet service providers (ISPs) are always changing the rules. Whether you’re using single opt-in or double opt-in, there will always be something new to learn.

But you’re a business owner, right? You don’t have time to learn what a spam trap is!

Well, I have good news for you.

My team at The Email Marketers knows it all, and we’re ready to help you! Schedule a call today, and we’ll discuss how a group of dedicated experts can make your email marketing service work for you. And don’t forget to check the rest of my blog for more email marketing tips and tricks.