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Email Deliverability: What It Is and Why It Matters


Email marketers spend hours crafting the perfect email campaign all while agonizing over every detail. And there’s nothing more defeating than finding out your hard work took a sharp detour—directly to the junk folder. Email deliverability helps you measure how often your emails are landing in the inbox instead of being labeled as spam—helping you refine your approach and get in front of key audiences.

Email deliverability matters and not just because you want your messages to be seen. Low deliverability, specifically a systematic deliverability issue, has a ripple effect. It can impact your branding, engagement rates, and ultimately, your ROI—which has much larger implications for your business. 

We have put together a plan to improve and maintain your strategy on your own email deliverability journey. 

What factors affect email deliverability?

Several factors affect an email marketing campaign’s likelihood of being successfully delivered. Emails must clear a series of checkpoints to be deemed safe and secure for delivery. In order to ensure success, these obstacles must be considered long before launch.

It’s important to take a calculated, proactive approach, whether you’re just getting started or working to undo poor performance. We have outlined ways to check and resolve spam filter trap issues that will result in seeing email success.

Email volume

Mailbox filters run on algorithms that monitor send volumes and trends over time. An email warm-up identifies you as a reputable account by gradually increasing your email send limit. Since a quick uptick in volume may cause your messages to hit the spam folder, a ramp-up period will help you maximize campaign effectiveness.

There are a variety of reasons to consider an email warm-up. They may include:

  • Getting started with or switching email service providers (ESP) 
  • Rebranding due to an acquisition or merger
  • Moving from a shared to dedicated IP
  • Migrating to a subdomain for email
  • Unusually high spike in email volume – think Black Friday sales or special promotions
  • You’re doing an email reset due to previous deliverability issues

Send frequency 

Email reputation is slow to build and quick to lose. As you start to send regular emails, be mindful of your frequency. Overwhelming readers with too many messages could result in unsubscribes and potential spam filter notifications for excessive messages. 

Unless you are a known daily sender (think e-commerce) send frequency should be once or twice a week. It’s also best to be transparent about any plans to increase frequency (like daily communication for holidays or promotions) by asking subscribers to opt-in to receive more emails. Subscribers will then anticipate and welcome your communication. 

Email content and format

Email content also plays a factor in determining email deliverability. While its impact is smaller, make sure your subject line, preheader text, body content, and images are relevant. Internet Service Providers (ISPs) have built-in filters to help identify spam and divert it from the inbox. 

It’s best to avoid using “spammy” language and formatting. These may include:

  • Enticing phrases such as “Click here!” or “Buy now!”
  • Multiple special characters in a subject line like “Big sale! Come check it out!!!”
  • All caps—it can give a high spam score and can seem aggressive.
  • Image-only email that can be marked as spam without real content to scan.
  • Links that look like phishing attempts.
  • Using link shorteners.

Ways to improve deliverability 

Email deliverability is too important to leave to chance. Your two main levers to ensure email marketing campaign success are increasing engagement and reducing spam complaints. With proper email infrastructure, inbox service providers (ISPs) will recognize you as a reliable sender. 

Here are some best practices to keep on your radar to maintain or improve effectiveness.

Make emails personal and engaging

Email subscribers opt-in to receive your messages because they trust and value your brand. Creating personalized emails makes them feel like each message has been created with them in mind. This increases engagement, conversions, and brand loyalty. 

Using a first name is great at getting attention, but subscribers have come to expect more. Combining segmentation and personalization is a powerful way to meet people where they are in the consumer journey and learn more about them to tailor future messages. 

Dynamically populating your messages with product references, exclusive offers, weather-related content, or interactive polling is a great way to tailor your emails for increased personalization.

Practice good list hygiene

Email list hygiene is a multi-step process that should be assessed regularly. It’s important to clean your email subscriber list to avoid sending messages to bad or non-existent email addresses.

Here are some simple ways to improve your list health: 

  • Ask subscribers to add your email address to their contact list – helping you avoid being sent to spam.
  • Include an unsubscribe option in every email to ensure you have an engaged audience.
  • Use double opt-in to help ensure subscribers are using their own email addresses and that those email addresses are valid.
  • Implement a re-engagement strategy to remove any inactive email addresses. Inactive addresses cause harm to your email reputation and even hit spam traps, causing deliverability issues. 

Check your sender reputation

Your sender reputation can influence email deliverability. You should proactively keep a close eye on your analytics to catch issues faster. Check key elements across critical areas like configuration, IP reputation, and authentication. This helps you address any underlying issues that may be hurting your deliverability.

You should also investigate further if you see any of the red flags below that could indicate a bigger issue:

  • A rise in spam complaints. This is a sign that something about your content isn’t resonating and could get you on a blocklist. 
  • An increase in bounce rates. While bounce rates determine your delivery rate, anything that harms your email reputation could hinder deliverability. 
  • A decline in opens and/or clicks. The occasional lackluster campaign is okay, but downward-trending engagement could lead inbox service providers to believe your emails are low-quality. 

Email deliverability testing 

Email testing should be top priority for deliverability. With email still being the cornerstone for marketing strategies, its success can be vital to your organization and your brand reputation. 

Since your audience has opted-in to receive your emails, they are comprised of your ideal customers. Running an A/B test set up the right way can help you learn what resonates the most and where improvements can be made. Will changing the call-to-action (CTA) button increase conversions? Is the copy informative, compelling, and prompting the action you’re wanting recipients to make? There’s always room to evolve your email to be more engaging and less spam-worthy. 

Deliverability can feel challenging with so many factors in play, but it’s a critical part of a healthy email marketing program. If your emails are taking a detour on the way to the inbox, your efforts—and marketing dollars—are being improperly used and could lead to unfavorable outcomes. 

Taking the extra steps to understand the factors that go into successful email deliverability and implementing best practices for your email marketing campaigns set you up for long-term success to maximize your efforts—and your results.


Make it to the inbox—not the junk folder

70% of emails show at least one spam-related issue that could keep them from reaching the inbox. Litmus Spam Testing scans your emails against 25+ different tests, identifies any issues, and provides actionable advice on how to fix them.

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