Email Deliverability Best Practices: How to Stay in the Inbox (and Out of Spam)

You put too much work into building an email list and creating incredible content for it to go unseen by a large percentage of your list.

For many senders, the silent killer that slowly drags down your email ROI is deliverability. It usually happens over time, making it easy to attribute declining engagement and revenue to stale content or an unengaged list.

However, deliverability can be reversed, although it’s much easier to maintain it than to repair it.

What is Email Deliverability (And Why it Matters)

No matter how great your content or how targeted your list, emails to spam folders are useless. 

Delivery vs Deliverability

Email delivery means that the email can be delivered. This usually means two things:

• The email address didn’t bounce (i.e., it’s a legitimate email).
• Mailbox providers (e.g., Gmail) decide to allow your email through.

Email deliverability, on the other hand, indicates the percentage of delivered emails that reach the inbox without being filtered into spam or junk folders (also referred to as “inboxed”). If an email goes to a non-Primary tab, such as Promotions or Social, that still counts towards email deliverability.

The Cost of Poor Deliverability

The obvious downside of unseen emails is the missing opens, clicks, and conversions. Imagine sending out 100,000 emails with each send, and expecting around 2,000 clicks each time.

Now, what happens if your deliverability drops just 10%?

You’ve potentially lost 200 clicks with each email that you send!

With 59% of B2B marketers reporting email to be their best channel for ROI, you likely can’t afford a drop in clicks without severely hurting your overall company margin.

Additionally, that 10% drop typically won’t remain at 10% unless you take steps to improve it. Your deliverability has fallen for a reason, and things will get worse if left alone—similar to going to the doctor and getting poor results on your blood work.

The Foundations of Good Deliverability

The time to install these best practices is now, before you experience significant issues. 

1. Put Your Subscribers First

As you consider your overarching email strategy, start asking questions like:

• “What do my readers expect from my emails?”
• “How often do they expect my emails?”
• “What is the most useful thing I can send?”
• “Why are you sending this email?”

Now, this doesn’t mean you can’t sell—there are certainly times for that. For example, new subscribers often opt in specifically to learn more about your offer. Tell them about it!

However, after that first week or two, you’re going to create much better long-term engagement with content-first, engaging newsletters. Emails that mostly pitch won’t nurture your subscribers for the long term.

2. Create Engagement Opportunities

The very best signal to mailbox providers is a subscriber base that opens, clicks, and engages with your emails.

With readers spending less than 9 seconds per email, how do you get your subscribers to open and interact? 

Here are a few ideas :

• Polls
• Surveys
• Quizzes
• Podcasts
• YouTube videos
• Links to relevant content
• Infographics
• Asking for replies

There are dozens of ways to increase email engagement—pick a few that make sense and start sprinkling them into your emails.

The more engagement you create, the more likely mailbox providers are to deliver your emails to Primary tabs.

3. Create High Quality Content

In addition to adding interactive elements, ensure that your overall content quality is high. Consider the following:

• Desirability - Is this the content that subscribers want at this time?
  
  
• Feedback Loop - Check engagement metrics, such as clicks, replies, and survey answers to find your best topics.
  
  
• Balance Text-to-Image - Excessive images can signal to mailbox providers that a message is potentially spam. While informative, quality images are additive, too many (or few images with little text) can hurt your sender reputation.
  
  
• Avoid Spam Words - Don’t overhype or come across as too promotional. The more you can write in a natural, helpful way, the more your readers will engage. Here’s a list of 188 spam words to limit in your copy.

4. Authenticate Your Emails

The basic technical foundation for your email sends is to ensure SPF, DKIM, and DMARC are set up correctly. Some refer to these as the passport, visa, and customs of email marketing, because they all serve separate but complementary functions in getting emails delivered.

• SPF -  Sender Policy Framework tells the mailbox providers which domains and IP addresses can send email on your behalf. This way, anytime you send an email from @yourdomain.com, Gmail and others know that it’s coming from you.
  
  
• DKIM - DomainKeys Identified Mail uses a digital signature to ensure that the email wasn’t modified during delivery. It was sent by you, and no one tampered with it.
  
  
• DMARC - Domain Message Authentication and Reporting Conformance defines what mailbox providers should do with your email if it fails authentication. Here’s a primer on the three DMARC policies you can set up, and which makes sense for you.

5. Maintain a Clean List

The more unengaged, outdated, or inactive addresses you send to, the more your sender reputation suffers.

Install list hygiene practices now, as fixing this later can be a huge undertaking. 

Here’s what you can do:

• Verify all new email addresses - Many email marketing companies partner with list validation services. Ensure that yours does this, or that you’re running your new leads or imported lists through a service like ZeroBounce.
  
  
• Delete unengaged contacts - If subscribers don’t engage for an extended period, they’re hurting your deliverability. Delete subscribers who don’t open or click for around 12 email sends.
  
  
• Avoid adding cold lists - Whenever you bulk-add subscribers who aren’t expecting it will result in higher unsubscribe and spam rates. This could be old clients or leads, a purchased list, or a new brand you’ve acquired. Add them slowly.
  
  
• Use double opt-in - It’s a simple way to ensure every email is real by requiring
  
  
• Have an obvious unsubscribe link - Not only is it legally required to have an unsubscribe link, but you want readers to be able to do it easily. According to ZeroBounce, 47% will submit a spam complaint if the email doesn’t have a way to unsubscribe.

Technical Best Practices for Email Deliverability

Now that we’ve covered the basics, let’s dive into the more advanced technical side of getting your emails delivered with consistency

Use a Custom Sending Domain

Many ESPs allow you to send emails using a shared sending domain (e.g., @beehiiv.email). However, this can hurt deliverability for a few reasons:

• No control over reputation - You’re sharing the same sending domain as thousands of others. They may be sending spam, which can hurt your deliverability as well.
  
  
• Less trustworthy - You look less like a real company and more like an unprofessional individual.
  
  
• No alignment signals - Mailbox providers prefer aligned domains where you’ve set up SPF, DKIM, and DMARC. You can’t do that with someone else’s domain.

Instead, use your own custom sending domain, such as John@YourDomain.com. 

Warm Up New Domains and IPs

If you’re starting out with email, switching domains, or launching a new brand, you may need to send emails from a new domain or IP address.

However, you won’t have any sender reputation built, and mailbox providers will watch with a closer eye than ever. A new brand sending to a large list screams spammer.

In these cases, you need to warm up your new domain before sending significant amounts of email. This way, it appears more natural to Gmail, Outlook, and other email clients.

Here’s an example schedule of how you could ramp up sending when you have a decent-sized list:

Note: The exact pacing depends on your list size, engagement, and what your monitoring tools tell you. Slow and steady always wins. If the above schedule results in high spam or unsubscribe rates, pull back.

Many brands choose to be extra cautious, understanding the importance of maintaining a high sender score. You could extend this schedule for a few months rather than 20 days.

Monitor With Tools

To fully understand and monitor, there are a few different tools you’ll want to consult with regularly:

• Google Postmaster Tools - This free service provides insight into the health of your email campaigns sent to Gmail users. You’ll see spam rate, domain reputation, message authentication, and more. If your Gmail looks good, you’re likely in good standing with other mailbox providers as well.
  
  
• MXToolbox - This popular tool is helpful for email and DNS diagnostics, providing information about blacklist monitoring, connectivity, and server response times.
  
  
• GlockApps - Gives you insight into inbox placement, showing you where your email lands across various inboxes and tabs.

By continually tracking your reputation, ideally you’ll be able to catch deliverability issues before they start to affect your actual inbox placement.

Common Deliverability Myths

Let’s debunk some common beliefs that newsletter senders often have.

Myth #1 - Great Design Trumps All for Deliverability

For some brands, great design leads to engagement. If you’re sending emails for Domino’s, you’re more focused on creating irresistible images of pizza than anything else.

Even so, Domino's still must get engagement with their emails, or they’ll get dinged by mailbox providers.

Engagement always beats out design.

Myth #2: Spam Comes from Spammers

It’s common to think about spam as coming from bad actors trying to steal your credit card information. 

In reality, spam often originates from legitimate senders with good intentions. Sometimes they forget deliverability best practices and do things like:

• Add a high number of cold subscribers to an email list all at once.
• Send off-topic emails.
• Pitch too often.
• Be overly enthusiastic in promoting a product or service.

Myth #3: Authentication Guarantees Deliverability

While authentication protocols are a critical part of your email program’s foundation, it’s just a first step. 

You still need to keep your lists clean, get good engagement, maintain low unsubscribe and spam rates, and monitor tools that track your sender reputation.

Final Thoughts

Deliverability isn’t a one-time, set-and-forget activity. It’s an entire strategy that senders need to be aligned on and actively monitor.

By combining technical trust with audience respect, you’ll stay on the right side of mailbox providers’ algorithms. The outcome is more conversions and more sales, making the reward worth the effort many times over.

At Letterhead, we’ll be your partners in increasing conversions across all your media brands. Schedule a time to chat, and we’ll show you how we help grow ROI.