Mastering Email Spam-Proofing

Sep 6, 2023 | Blog, Deliverability

In today’s era of digital connectivity, email communication has become an indispensable component of both our personal and professional lives. However, there’s nothing more frustrating than crafting a well-thought-out email only to find it buried in the recipient’s spam folder. To ensure your messages reach their intended recipients, it’s essential to understand the factors that contribute to emails being marked as spam and implement strategies to avoid this fate.

Once email clients (such as Outlook and Gmail) detect more of your emails as spam, your reputation will gradually get worse over time. And a bad reputation will lead to more emails ending in the recipients’ spam folder.

In this article, we’ll explore 10 proven strategies to help you prevent this from happening by keeping your emails out of the spam folder and maintaining a good email reputation.

1. Use a Reputable Email Service Provider (ESP)

One of the first steps in avoiding the spam folder is to choose a reputable Email Service Provider (ESP). ESPs with a good track record invest in maintaining their servers’ reputation, making it less likely that your emails will be flagged as spam.

2. Authenticate Your Email

Email authentication methods like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) help prove the legitimacy of your emails. Implement these authentication protocols to enhance your email’s credibility.

 3. Build a Clean and Engaged Email List

A key factor in spam detection is the quality of your email list. Never use purchased email lists or outdated ones. Instead, build a clean and engaged list organically by asking for explicit consent from your subscribers and regularly cleaning out inactive addresses. When recipients are inactive, your reputation among email clients will gradually get worse. One the fastest and easiest way to get rid of inactive recipients is by handling your soft and hard bounces.

4. Craft High-Quality Content

Spam filters analyze the content of your emails, searching for red flags like excessive use of capital letters, excessive punctuation, and certain trigger words. Craft your emails with high-quality content, avoid spammy language, and provide value to your recipients.

5. Monitor Your Sending Frequency

Sending too many emails in a short period can trigger spam filters. Be mindful of your email sending frequency and segment your list to target specific recipients with relevant content. By segmenting, you make sure that the right people receive the right emails – by doing so, you can make your messages more relevant and effective, and you can minimize the total number of emails each person receives.

6. Avoid Using Misleading Subject Lines

Misleading or deceptive subject lines are a common reason for emails ending up in the spam folder. Make sure your subject lines accurately reflect the content of your email to maintain trust with your subscribers, and to avoid that they mark it as spam.

7. Optimize HTML and CSS

Improperly formatted HTML or CSS can trigger spam filters. Ensure your emails are well-structured and free from broken links, missing images, or excessive coding errors.

8. Include an Unsubscribe Link

Always provide an easily accessible and functional unsubscribe link in your emails. This not only complies with GDPR regulations but also reduces the chances of recipients marking your messages as spam. Additionally, email clients will look for an unsubscribe link when scanning and evaluating your email.

9. Monitor Your Sender Reputation

Keep a close eye on your sender reputation by regularly checking your email deliverability and open rates. This will help you detect and address any issues that could affect your emails’ placement in the spam folder.

10. Test and Monitor

Regularly test your email campaigns using spam-checking tools and conduct A/B tests to see what works best for your audience. Continuously monitor your email performance and adjust your strategies accordingly.


Avoiding the spam folder is crucial for successful email marketing and communication. By following these 10 proven strategies, you can significantly reduce the likelihood of your emails being marked as spam and ensure that your messages reach their intended recipients.

Remember that maintaining a good sender reputation and adhering to best practices in email marketing is an ongoing process that requires diligence and a commitment to providing value to your subscribers.

Heysender blog

Read our other blog entries to get new inspiration for your transactional emails.

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