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Why Emails End Up in Spam and How to Avoid It: Reasons and Recommendations

Email marketing
November 10, 2022
13 min

Email marketing is a powerful tool for reaching the target audience and expanding the client base.

According to SaleCycle, 59% of respondents say that an email newsletter influences their purchasing decision, and approximately 50% of people shop via email at least once a month. On the contrary, 15.8% of all emails go to spam.

How do you know if your email goes into spam? What are trigger spam filters? And how to prevent subscriber churn?

In this article, we will look at the most common reasons and share the rules, following which your emails will not get lost, and the opening rate will be higher.

What is a Spam Filter?

The spam filter is a system that detects dangerous or unwanted emails and keeps them out of your inbox.

Take into account that different spam filters have various approaches to evaluating content as spam. As a result, your email may get to the inbox of one customer, and end up in the spam of another. However, all spam filters have one thing in common — they ensure the safety and cleanliness of the recipient’s mailbox. Therefore, if an email goes in spam, it has been determined as dangerous or unwanted content for some reason.

Let’s figure out what the reasons are for emails going to spam!

Reasons for Emails Ending Up in Spam

Lack of authentication

One of the main reasons for emails being determined as spam is their non-correspondence to the email authentication standards. These are digital signatures implemented so that the mail system can identify which emails should be sent to the “Inbox” and which to “Spam”.

Lack of or incorrect authentication settings is the most common reason for emails going to spam. Hence, it is important to set up the following settings:

emails in spam

Important. If you don’t set up DMARK, scammers will be able to send spam using your domain, which may damage the domain’s reputation.

Domain reputation

Each domain has its own history and reputation. As spam filters evaluate your emails, they give more value to this data. Users do not see emails with a bad domain reputation, which causes a fall in the open rate and a drop in the email campaign efficiency. Besides, the probability of getting into spam is also very high.

To find out if a domain’s low reputation is the actual reason why your emails get to the spam folder, you need to follow the recommendations:

  • Check the reputation of your domain. For this matter, you may use the Postmaster tool from Google.
  • Check your domain in the block list.  MXToolBox and multiRBL are popular services for checking multiple block lists at the same time.

In case you find out that the domain’s reputation is at a poor level, consider the recommendations of the Retention Marketing Team Lead at Promodo Yulia Kuryk:

  1. Narrow the segment. Send emails only to a base of people that have been actively reading your emails in the last 2-3 weeks.
  2. Send emails only using the “Limited Sending” function. Do not mail to everyone at once. Try sending 100 emails per hour, for example.
  3. Check every email with MailTester. You will be able to see errors in the design of the newsletter. For example, unsigned images, too much text, too large weight of the email, etc.
  4. Turn off a reactivation. While repairing the reputation, it is better to disable reactivation and leave only behavioral scenarios, such as “adding to the cart” or “abandoned viewing”.

IP address reputation

The same as a domain, the sender’s IP address also has a history that is tracked by email systems. For example, a small number of spam complaints and an insignificant bounce rate make the sender’s IP address more reliable.

When an email is sent via a public IP address, its reputation is not only based on your sending activity, but also on the habits of all senders. Problems with IP reputation occur rather rarely,  although if your email does end up in spam, then:

  1. Check your IP address in the block list. The MultiRBL tool can also be used here.
  2. Contact your email service provider (ESP). Find out if they have any information about what caused it and what they can do to fix it.

Link shorteners and open URLs

Often, senders use shorteners such as as one simple means of tracking link clicks. On one hand, it is convenient, but there’s also a considerable disadvantage, namely link shorteners make it easy to hide harmful websites or virus files. Therefore, if you use link shorteners, spam filters may mark your email as spam or block it.

Such an approach can also be applied to open links in email. Spam filters have discovered a pattern of using open URLs and spam, so it’s better not to use them. Also, hidden links look more attractive from the UI perspective. For example:

emails in spam

Both sentences send the reader to the article in the blog. However, the first one has a hyperlink to Promodo’s blog, and the second one uses an open URL. The first option is definitely more suitable for a successful retention marketing campaign.

“However, shortened links are not always evaluated as spam by mailers. For example, almost all services, when composing “raw links” with UTM-tags, shorten them, but under their domain. Spam filters do not respond to such links because the domain has a good reputation”. Svitlana Fursa, Head of the Retention Marketing Department at Promodo


Spam filters check emails that contain attachments especially carefully. Usually, viruses may hide in ZIP files, malicious macros are in Word, or phishing links are put in PDF files. So if you need recipients to download a file, don’t attach it to the email. It’s better to make it available on your website. It’s just a few extra clicks, but it will increase the likelihood that your email will end up in the inbox.

Spam words

If your email is in spam not because of a bad domain reputation, authentication, or other factors, check whether the text contains the spam filter trigger words and expressions, especially in the subject of the email. Examples of such spam filter triggers are “buy”, “sale”, “order”, “near you”, “extra income”, “earn extra money”, “best price”, and “free” which are classified by spam filters as “spoetry”.

Spoetry is randomly generated text that spammers use to trick recipients. Besides, spam filters trigger words, it also includes caps lock, redundant punctuation, etc.

Mailing base

The main task of spam filters is to remove content that is not interesting to users, so to maintain a high level of delivery, target the newsletter to those subscribers who are really interested. We provide you with basic recommendations concerning the choice of mailing base:

  1. Never buy or borrow email databases. Even though it does not affect sending your emails to spam directly, it still worsens your reputation.
  2. Add to the database only people who have agreed to the mailing. For this matter, you can use the two-step subscription system (double opt-in).
  3. Remove unsubscribed recipients. Carefully monitor the number of rejections in emails. Even if subscribers didn’t unsubscribe, although they do not interact with your emails for a while, they may have marked them as spam.

Following the list of offered recommendations, Promodo’s team managed to decrease the number of contacts in the email database from 44,000 to 23,000 contacts for the largest ski resort in Eastern Europe Bukovel. Such an approach allowed generating 850 transactions from the email channel for 9 months and gaining 55% of loyal subscribers.

Recipients mark your emails as spam

The more users mark your emails as spam, the more likely future emails will end up in the spam folder.

How to understand that the email went to spam? Use Postmaster Tools to track both overall domain reputation and spam metrics. Use GlockApps for a more detailed analysis of the reasons why emails went to spam.

“The most common reason for an email to end up in spam is the bad location of the Unsubscribe button or its absence. If customers cannot opt-out of a mailing, they often mark it as spam. And the more often this happens, the worse the reputation of the domain”. Svitlana Fursa, Head of Retention Marketing Department at Promodo

If you want our specialists to provide you with a more detailed consultation, just fill in the request form!


If you’ve used our checklist and investigated your email marketing strategy, although you are still not satisfied with its results, probably your customers stopped reading your newsletters.

We have developed recommendations based on Promodo’s professionals’ expertise to improve the effectiveness of your emails.

FOllow the frequency of release

emails in spam

Daily mailing is the synonym for annoying mailing. As a result, too often emails will start to be perceived as spam, no matter how perfect they are. To keep the IP address “warm”, evenly distribute the number of mailings and make a schedule for their output.

Choose the segment precisely

Check whether everything fits in the context of the “topic-audience segment”. For example, when reactivating the segment that has not read the newsletter for more than six months, the opening percentage will be rather low. Hence, there’s no point in emailing. On the contrary, you may create a separate segment for those who do not read for a month or two and send them the most attractive offers, such as new arrivals, discounts, Black Friday offerings, etc.

“Abandoned cart”, “abandoned view”, and “happy birthday” types of email demonstrate the best performance in behavioral and personalized trigger emails. They always have higher opens, clicks, and conversion rates”. Svitlana Fursa, Head of Retention Marketing Department at Promodo.

Create the UX/UI tools

Try to add “voting” such as Interesting/Not interesting in each email. If a person clicks Not Interesting, add them to a separate segment with transactional mailings. Those who chose Interesting need to be added to the active base.

What is more, using the “voting” principle, you should give subscribers the opportunity to customize their subscriptions. For example, to receive letters twice a week and only in certain categories.

Test gamification

Gamification cannot affect the open rate significantly, although it does impact conversions and sales. The more exciting the game mechanic is, the higher the percentage of engagement and retention will be. With the help of puzzles, rebuses, roulette, or other mechanics, you can increase the click rate by 1.5-2 times.

Using the AMP For Email technology, Promodo has managed to reach 38% of the click rate, due to the implemented roulette gamification for Karcher. Check the full case study here.

We hope that our recommendations will help your emails get to the inbox only. Do you have any questions? Our Retention Marketing department is ready to answer them.

Schedule a Free Consultation

Written by
Maria Kashina

Content Marketing Manager at Promodo

November 10, 2022
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