In email marketing, getting your campaign to spam is considered a chief evil. However, believe it or not, a letter in a spam folder is not the worst that can happen to your emails. There’s another scenario – the one where none of your letters are delivered in the first place. It means that there’s no way for a reader to open or as much as see the email.

Since it’s crucial for business owners and email marketers to make sure messages make it to inboxes, campaign managers pay a lot of attention to deliverability. In this post, you will find out which mistakes you make can keep your email from a spot in a reader’s inbox and discover simple ways to improve email delivery.

Explaining Email Deliverability

Email deliverability is the ability of a letter to get from the sender’s email client interface to the recipient’s inbox. According to statistics, a good deliverability rate of a campaign is 95% – anything lower than that means that you are using a compromised account or are targeting an unengaged audience.


What determines email deliverability? Typically, to evaluate the delivery rate, email marketers take the following into account:

  • Bounce rates – the number of emails that can’t reach readers either because the email is invalid (hard bounce) or because the recipient is temporarily unavailable (soft bounce).
  • Open rates – contrary to the popular belief, it’s not enough for a reader to click on an email to count the action as an “open”. Open rates are calculated based on the number of readers who choose “Enable images” when viewing the letter or click on in-mail links.
  • Spam complaints – highly impactful for deliverability, spam rates show how many people flag your messages as spam after receiving them. As a rule of thumb, marketers strive to keep spam rates between %0.1 and 1% – a higher value is a red flag that requires reviewing the email list or revisiting the campaign’s copy.
  • Engagement is the most important metric in email deliverability. When evaluating sender addresses, ESPs assess how end-users interact with an email. If a user didn’t open messages, click on links, or enable image display, email client providers understand that the audience isn’t interested in a message. After a while, an ESP will cut passive users off and stop delivering your emails to them.

Top 9 Mistakes That Cost You Email Deliverability (And Ways to Get Rid of Them)

There are dozens of factors determining email deliverability – from the robustness of your email infrastructure to the content you share with uses. At any stage of campaign design, it’s easy to make mistakes that, if repeated, will take your sender reputation and lead to readers never seeing your message again.

The good news is, as long as you are aware of the most common issues that cost marketers campaign deliverability, you can fix them and make sure you are sending emails out responsibly.

Let’s take a look at 9 deliverability killers and the ways to get rid of them once and for all.

Campaign management

1. Inconsistent email volumes

Sending thousands of volumes one week, giving up, and coming back to the inbox in a month with another email blast is the easiest way to get ESPs to be wary of your address.

Fix: Through trial and error, marketers realized that a successful enterprise email marketing strategy is a series of targeted and consistent efforts. Having a fixed schedule is key to high email deliverability – be sure to implement one.

How many emails should a business owner send? According to statistics, most Internet users expect to see promotional emails from one company weekly.


Newsletters and how-to messages, on the other hand, can have a higher frequency – send these out 2-3 times a week.

2. No email authentication

Although email marketers are rarely well-versed in tech, paying attention to the technical infrastructure of your account is crucial for high deliverability. Unfortunately, it’s common for business owners to miss out on setting up SPF and DKIM. Why are these important?

Fix: SPF (short for sender policy framework) is a record that protects an email from forgery or phishing. You can ensure that new messages can only be sent from your server, protecting the account from hijacking.


DKIM (short for DomainKeys Identified Mail) is another authentication method used to spot phishing. In a nutshell, DKIM contains a private and a public key – the former is stored in the DNS, the latter is saved on your hard drive.

Like SPF, DKIM helps make sure that a third-party attacker can’t use your email to send out spam and jeopardize the audience’s trust. Make sure to set up both of these authentication algorithms to win reliability points from ESPs.

3. Buying email lists

Luckily, the practice of buying email lists is not as popular as it once used to be – however, it’s often tempting for marketers to get access to thousands of emails and start sending out newsletters and transactional emails.

The impact of buying email lists is atrocious. Since readers never gave permission to get letters from you, the odds of them flagging the letter as spam are skyrocketing. As mentioned above, spam rates heavily influence deliverability, meaning that after a few low-performing marketing campaigns, ESPs will stop delivering messages from your account and domain altogether. Integrate social media with your email campaign using various tools like Facebook tools, Instagram tools, etc to get the best results for your email marketing campaigns.

Fix: set up an email subscription form on your website instead. To increase the odds of people joining, offer value in return – an e-book, a checklist, or a discount. Once a website visitor left his email, send him an onboarding letter to confirm his intentions – in marketing, this powerful strategy is called double opt-in.

4. Not letting unengaged readers unsubscribe

Did you know that most people don’t flag your emails as spam because they hate them and think that peace was never an option? The truth is, 43% of readers report messages because they found no way to unsubscribe.

So, even if removing or concealing the “Unsubscribe” link seems a logical choice for a marketer who doesn’t want to lose a hard-earned reader, giving the audience an option to live your list is crucial for high email deliverability rates.

Fix: make sure the “Unsubscribe” button is clearly visible. To give readers an option to reconsider their decision, add a poll to the letter that will allow the audience to redefine their preferences.

For instance, you should let people stop reading transactional emails if they don’t like them or tweak the frequency with which they get your messages. This way, the company will come across as thoughtful and caring, help improve customer service and you will retain more readers.


5. Spammy subject lines

When writing a subject line, most marketers are driven by the desire to impress the audience, capture readers’ attention, and make sure more people open the letter. However, over the years of sorting through emails, ESPs picked up on the habits spammers use to lure people into opening their emails. Unfortunately, the buzzwords like “Free” or “Discounts” that used to drive conversions 10-15 years ago, are now flagged as suspicious and destroy your account’s reputation.

Fix: here’s which words and phrases you should avoid when coming up with subject lines:

  • Free
  • Discount
  • Money, cash, price
  • Buy now
  • 50% off, 100% free
  • Double your earning and other empty promises.
  • Sex and pornography-related statements: online dating, viagra, etc.

Other than that, avoid using upper-case letters in the subject line – most ESPs mark these as spam.

6. Using URL shorteners

Similarly to trigger words in subject lines, using URL shorteners once was a recommended practice. This way, instead of publishing long and messy link, a business owner could share a good-looking URL.

However, spammers eventually started abusing shortened links. After being redirected to porn sites and promotional offers, people no longer trusted bit.ly and goo.gl links – neither did email client providers.

Fix: right now, staying away from URL shorteners is a safer bet for marketers. Instead, you can use an anchor and attach a link to a relevant part of the email content.

7. Not adding a plain-text version to an HTML email

Sleek and good-looking newsletter templates are memorable and can make a powerful impression on readers. There are companies that put so much soul in newsletter design that the audience appreciates every message as a work of art.


However, if your readers didn’t get emails from the company before, overloading the letter with HTML elements isn’t the right strategy since such messages are more likely to end up in “Promotion” or “Spam” tabs.

Even if a reader gets an email, an ESP might choose to disable the image display. Unless a user chooses “View images”, he will have no ways to see a full design – thus, missing out on buttons, copy you added to the visual of a proposal template, and other content.

Fix: email designs are a powerful part of creating a link between the campaign and the brand. If you don’t want to give them up for the sake of deliverability, it’s understandable. However, to make sure a reader can access all essential information even with disabled images, add a back-up plain-text version to an HTML email.


8. No mobile-friendliness

According to statistics, 68% of emails are opened on smartphones. Now that most Internet users are on smartphones to check inboxes and answer messages, optimizing your design for mobile devices is no longer optional – otherwise, you risk engagement losses, higher spam rates, and, consequently, lower deliverability.

Fix: before sending a campaign out, assess its mobile-friendliness. Here are the practices marketing collaboration teams follow to make sure that a letter is readable via smartphones:

  • One-column layout
  • Larger font size
  • Lower image resolution and smaller size
  • Links instead of buttons, separated by spaces.
  • The overall email width doesn’t exceed 600 px.

9. Including too many images

Visually-rich emails are flashy but, the truth is, they are incredibly slow to load. The fact that end-users will need a better network quality and more waiting time to see your email fully will impact engagement rates negatively.

Other than that, ESPs have animosity towards images – 5-7 years ago, spammers used to rely on visual content to bypass spam filters. That’s why, in 2020, emails that don’t respect the image-to-text ratio will get blacklisted automatically.

Fix: as a rule of thumb, use no more than 2-3 images in an email, keeping the letter’s total weight between 600-800k.


Email deliverability directly contributes to the success of your marketing activities. By setting up a strong defense mechanism against phishing, being mindful of the content you share and the way your emails are formatted are some of the best practices to keep a stellar deliverability rate.

Monitoring deliverability and determining which practices worked is another practice to help you reach readers without fail. As long as you are mindful about keeping a high delivery rate and have a clear set of guidelines to follow for each campaign, there will be no issues with landing into a user’s inbox.


****This is a guest post from Andriy Zapisotskyi. Andriy is a Growth Manager at Mailtrap, a product that helps people inspect and debug emails before sending them to real users. He has over 5 years of experience in the field of marketing & product. Andriy loves to network with people. Running is his hobby and he enjoys discovering new places. ****


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