Email marketing has become an essential tool for businesses to reach their target audience and promote their products or services. However, despite careful planning and crafting of engaging content, many marketing emails often find themselves relegated to the dreaded spam folder or the less conspicuous commercial email folder. This phenomenon has perplexed marketers for years, but it can be explained by a combination of factors related to email service providers, spam filters, and recipient behavior.

TL;DR summary

This article explains why marketing emails don't always land in recipients' inboxes but often end up in spam or commercial email folders. This phenomenon is influenced by complex factors such as spam filters, sender reputation, email content, authentication issues, recipient behavior, and the growing volume of marketing emails.

Actions to improve deliverability:

  1. Maintain a positive sender reputation by sending relevant and valuable content.
  2. Avoid excessive promotional language and spam-prone words in emails.
  3. Ensure proper configuration of authentication protocols like SPF and DKIM.
  4. Obtain explicit consent from subscribers and avoid sending unsolicited emails.
  5. Monitor and respond to recipient engagement to maintain interest.
  6. Follow email marketing best practices and avoid excessive email sending.

By following these actions, marketers can increase the chances of their marketing emails reaching recipients' inboxes rather than ending up in spam or commercial folders. This enhances the overall effectiveness of email marketing.

Spam Filters and Their Complex Algorithms

One of the primary reasons marketing emails end up in spam folders is the ever-evolving complexity of spam filters. Email service providers employ sophisticated algorithms that constantly analyze incoming emails to determine whether they are legitimate or spam. These algorithms consider various factors, such as sender reputation, email content, and user engagement.

Sender Reputation: Spam filters often assess the sender's reputation by examining past email behavior. If a sender has a history of sending spammy content or engaging in suspicious activities, their emails are more likely to be flagged as spam. Maintaining a positive sender reputation requires sending relevant and valuable content to engaged recipients.

Email Content: The content of an email plays a crucial role in its fate. Emails laden with excessive promotional language, numerous links, and images may trigger spam filters. Similarly, certain keywords commonly associated with spam, like "free," "discount," or "money," can raise red flags.

User Engagement: Spam filters also consider recipient engagement with emails. If recipients frequently mark emails from a particular sender as spam or simply ignore them, it signals to the spam filter that the content is unwanted. Therefore, marketers must focus on sending emails that recipients want to engage with.

Misconfigured Authentication and Technical Issues

Email authentication is another factor that can land marketing emails in the spam folder. Recipient email providers often use authentication protocols like SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to verify the legitimacy of an email's sender. If these authentication protocols are not correctly configured or if there are technical issues with them, it can lead to email deliverability problems.

With Maileon, managing and monitoring authentication (SPF, DKIM) to industry standards is done by delegating an account subdomain via DNS records.

Lack of Subscriber Engagement and Consent

Email marketing is most effective when it reaches an engaged and interested audience. When marketers send emails to recipients who haven't explicitly opted in or haven't engaged with previous emails, it can trigger spam alerts. In some cases, recipients may mark these unsolicited emails as spam, further harming the sender's reputation.

The Ever-Growing Volume of Marketing Emails

The sheer volume of marketing emails inundating inboxes is a significant challenge for email service providers and their spam filters. With countless marketing campaigns vying for attention, it becomes increasingly difficult for filters to distinguish between legitimate marketing emails and spam.

Changes in User Behavior

User behavior also plays a role in email placement. For instance, if a recipient habitually ignores marketing emails from a particular sender or rarely opens them, the email provider might automatically redirect those emails to the commercial email folder or spam folder. Be aware that with providers such as Gmail, behaviour of one recipient can impact the behaviour of the spamfilter for the next recipient. As a result, it becomes essential for marketers to continually engage and maintain the interest of their subscribers. Also consider to make filtering out low-interacting contacts from lists part of the email marketing strategy.


The journey of a marketing email from sender to recipient's inbox is influenced by a complex interplay of factors, including sender reputation, email content, authentication protocols, user behavior, and spam filters. Understanding these elements is crucial for marketers looking to improve email deliverability and ensure their messages reach the right audience. By focusing on delivering valuable content, obtaining explicit consent, and adhering to best practices, marketers can increase the chances of their emails landing in the inbox rather than the spam folder or commercial email folder, ultimately enhancing their chances of success in the world of email marketing.