The most common mistakes that cause brands to end up in the spam folder and how to avoid them

Email marketing opens up great business opportunities only when campaigns successfully land in recipients' inboxes and not in the spam folder. Based on the latest email deliverability statistics from GlockApps, the average spam placement rate across all internet service providers reached 22.85% in Q3 2024. That's why it's worth making an effort to reduce the likelihood of your emails ending up in spam, as it's crucial to your success.

In this article, we'll go over the top reasons why emails end up in the spam folder and provide tips on how to avoid them in your future email campaigns.

Common mistakes that cause emails to end up in the spam folder

As spam filters are constantly evolving and sophisticating their algorithms, it's becoming increasingly challenging to send emails straight to inboxes. To make it easier for you to adapt to the changes in the world of email marketing and achieve good results, we've summarized common mistakes that lead to emails ending up in the spam folder and provided useful tips on how to avoid them. Let's dig deeper.

1. Content issues

Сontent issues might include formatting errors, high image-to-text ratio, heavy templates, incorrect image display, large attachments, excessive use of spam trigger words and techniques, and broken or unverified links.

Sending an email with problematic content can ruin your marketing campaign and cause your company to lose money. After all, if your subscribers don't respond to your email, it will reduce the engagement level in the eyes of internet service providers (ISPs) and gradually damage your brand reputation, undermining trust in your future communications.

Tips to avoid email content issues:

• create engaging emails that encourage subscribers to interact, as modern spam filters evaluate user behavior;
• switch to a MIME format in your emails that contain both HTML and plain text to ensure maximum compatibility and reach;
• make your content concise and focused — readers don't have time for long, irrelevant texts;
• highlight one key message and don't overwhelm readers with numerous offers or updates;
• limit the number of links and make sure they are from reliable sources;
• use graphic elements wisely, maintaining a 60/40 text-to-image ratio and adding alt text for fast loading;
• maintain brand consistency with consistent content that aligns with your marketing strategy;
• keep your newsletters fresh by updating information and using email templates selectively;
• avoid overusing interactive elements such as large files or forms; instead, use links to web pages to explain more;
• create responsive email templates that adapt to different devices and screen sizes;
• avoid using spammy words to achieve the best results;
• make sure to include a visible unsubscribe link in your emails, as spam filters may flag emails without an easy opt-out option, and this can damage your sender reputation;
• thoroughly test your emails for spam before sending them out, as you won't be able to adjust them once they're sent.

2.   Failing to make emails accessible

When not all people can understand your emails, it's a bad scenario not only for them but for you as the brand that generated them.

Create accessible emails by avoiding overly complex layouts or content that not all users can easily interpret. This includes images without alt text, using only color to convey information, or designing content that excludes users with visual impairments, color blindness, dyslexia, or other conditions.

Ensuring your emails are accessible not only improves user experience but also helps you comply with global accessibility standards, such as WCAG 2.1 and ADA, which are required by various regulations in the US, the EU, Canada, and beyond.

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Tips to avoid email accessibility issues:

• optimize email content for voice assistants and screen readers;
• maintain sufficient color contrast;
• add alternative text for all images;
• choose legible fonts with appropriate text size;
• steer clear of using color alone to highlight information;
• use clear, descriptive link text;
• organize your emails in a hierarchical structure using headings;
• include descriptions for tables and define headings.

3.   Overlooking email personalization

Sending irrelevant emails is one of the most common email marketing mistakes that lead to spam complaints. People receive numerous emails daily, which is why the need to keep readers engaged is growing. Personalizing email copy for the recipient has become a default rule because when content is tailored to the user's interests, it increases engagement and conversions, improves behavioral factors, and positively impacts the sender's overall reputation.

Every day, brands collect and analyze a large amount of customer data, which is then integrated into their email campaigns. Check your inbox, and you'll likely find emails that are more or less relevant to your interests, which proves that personalization works.

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Personalization in email marketing

Tips to avoid email personalization mistakes:

• integrate the latest data analytics technologies with your marketing tools and CRM systems to better understand your customers and deliver highly personalized content;
• adding dynamic content to your messages can be a pleasant surprise for your customers and make your content even more relevant and noticeable;
• make sure that the tone of voice reflects your audience's preferences. Your offers should sound like a one-on-one conversation rather than a sales pitch;
• be helpful, assist your customers in achieving their goals and solving their problems, and show them that you care.

4.   Sending from a “no reply” email address

Usually, a "no reply" address is used for automated mailings, such as autoresponders, reminders, notifications, or important alerts. Their function is clear: to deliver information without the need for a response from the user.

Although they are useful and facilitate many processes, using a no-reply address for marketing emails can lead to a decrease in user engagement. Sending emails without a reply address makes it impossible to receive feedback, thus closing the opportunity for the brand to engage in dialog and build a relationship with the audience.

Tip to avoid this mistake: Use a controlled email address for email correspondence to receive responses or provide additional information to customers. This way, you can proactively identify potential problems, provide guidance, and address concerns about your service and offerings, improving engagement and avoiding being filtered into the spam folder.

5.   Incorrect email authentication

Today, email authentication has become a requirement of all major ISPs. This set of methods and protocols is used to verify the legitimacy of an email, ensuring that it came from the stated sender and that important information has not been altered during transmission. Authentication mechanisms are crucial in preventing email fraud, phishing, and unauthorized use of company email accounts.

The main email authentication methods include the DKIM, SPF, and DMARC protocols. Publishing a DMARC record in DNS allows a domain owner to monitor who is sending emails on behalf of their domain. By having all the detailed information about its email channel, a business has full control over it and can thus ensure that customers receive original emails.

Eventually, DMARC helps improve not only email security but also performance. Companies that configure authentication correctly see an increase in email delivery rates.

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How to improve deliverability with email authentication

Tips to pass email authentication checks and avoid email spam filters:

• publish an SPF record for your domain. Most email service providers (ESPs) will supply the value to include in this record;
• enable DKIM signatures for your emails. Typically, this is managed by your ESP — you just need to switch it on for your outgoing emails;
• publish a DMARC record for your domain. Use tools like GlockApps DMARC Analyzer to create a DMARC record easily;
• set up a custom return-path domain. Some ESPs allow you to use your own domain for the return-path, which aids in SPF alignment and DMARC authentication;
• configure reverse DNS records. This is especially important if you're setting up your own mail server, as it ensures that the sending IP address can be matched to the sending domain.

6.   Deliverability issues

Senders often need to pay more attention to potential email deliverability issues. However, poor performance can mean that all email marketing efforts are wasted and emails end up in the spam folder.

Sending IP address issues can significantly impact email deliverability:

• if your IP address is blacklisted — whether by the recipient's email service provider or public blacklists like SpamCop or Spamhaus — your emails may be blocked.

Although IP address reputation is important, the reputation of the sender's domain often carries more weight:

• if you're using shared IP pools, your domain is unique to you, so your sending habits directly affect your domain's reputation;
• a low domain reputation can lead to emails being filtered into the spam folder.

Domain reputation is built over time based on several factors:

• user complaints;
• spam placements;
• emails sent to invalid addresses;
• suspicious sending patterns;
• overall user engagement.

To avoid spam filters and keep your domain reputation strong:

• focus on maintaining good content;
• practice solid sending habits;
• foster positive interactions by encouraging users to reply to your emails.

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Tips to improve email deliverability

Tips to avoid email deliverability issues:

• identify and fix email deliverability issues on time. The sooner you find and resolve the problem, the less damage will be done to your marketing campaigns. Therefore, the main question is not whether an issue will occur but when it will be noticed and resolved. Regularly test your email deliverability to detect undeliverable emails promptly;
• run tests to see how your emails perform with major providers. Check if your emails are blacklisted and take steps to work on their removal if needed. ​​You can also monitor key factors such as email authentication, spam scores, sender reputation, and content analysis to receive actionable insights for improving your inbox placement;
• run automatic spam tests for the most important emails and get instant notifications if your inbox falls below the desired value;
• stay up-to-date with the latest updates from senders, guidelines, requirements, and spam filtering technologies to maintain good metrics and stay compliant;
• use dedicated tools to test your messages and gain full control over the success of your email marketing campaigns.

Wrapping up

The common reasons that email providers consider when sorting emails are the reputation of the sender's domain, the email content, and the user interaction. Each provider has its own algorithm and decides the importance it assigns to a particular factor. Therefore, addressing the spam placement problem is often a much more complicated process than fixing certain errors in the template.

In this article, we've covered the main mistakes that lead brands to the spam folder and provided useful tips to avoid them. Consider them carefully and make the necessary adjustments to your strategy so as not to trigger spam filters.