Mastering the Inbox: 10 Tips for Crafting Emails That Will Pass Spam Filters


In the digital age, email is an essential communication tool for businesses and individuals alike. However, the increasing prevalence of spam has led to more stringent filtering systems, making it harder for legitimate emails to reach their intended recipients. In fact, it’s estimated that 45% of all emails sent are considered spam, causing businesses to lose an estimated $20.5 billion annually due to decreased productivity and technical expenses (source: The Radicati Group). To ensure your emails don’t end up in the spam or junk folder either, we’ve compiled 10 tips for crafting emails that will pass spam filters. By following these guidelines, you can increase the chances of your messages landing in the right inbox, allowing you to communicate effectively with your audience. Along with this, it is also important that you warm up your IP effectively as it is an important part of email deliverability.

Choose a Reputable Email Service Providers

One of the most important factors in avoiding spam filters is using a reputable email service provider (ESP). These providers have established relationships with ISPs and have systems in place to ensure your emails are delivered. Some popular ESPs include:

As marketing expert Neil Patel notes, “Choosing the right email service provider is like choosing the right partner. They should support your goals, be reliable, and help you effectively reach your audience.” By selecting a reputable ESP, you’re taking the first crucial step in ensuring your emails pass spam filters.

Create a Compelling Subject Line

Your subject line is the first impression recipients get of your email, and it plays a crucial role in whether your email passes spam filters. According to a study by Convince & Convert, 35% of email recipients open an email based on the subject line alone. Crafting a compelling subject line is both an art and a science. Here are some guidelines and examples to help you create effective subject lines:

  1. Keep it short and relevant: Aim for 6-10 words in your subject line to ensure it’s easily readable on various devices, including mobile phones. Make sure the subject line accurately represents the content of your email. For example:
    • “Boost Your Sales with These Proven Strategies”
    • “5 Easy Ways to Improve Your Fitness Routine”
  2. Evoke curiosity or a sense of urgency: Creating a sense of urgency or curiosity can entice recipients to open your emails. However, avoid making false promises or using clickbait tactics, as this can harm your sender reputation. Some examples include:
    • “Last Chance: Register for Our Webinar Today”
    • “Unlock the Secrets of Successful Entrepreneurs”
  3. Use numbers and lists: Subject lines that include numbers or lists often perform well, as they promise concise and easy-to-digest content. Examples:
    • “7 Tips for a More Productive Workday”
    • “Top 10 Travel Destinations You Must Visit in 2023”
  4. Ask questions or create a personal connection: Engage your audience by asking questions or using personalization, such as the recipient’s name or location. Examples:
    • “John, Are You Ready for This Exclusive Offer?”
    • “How Can You Maximize Your Savings in 2023?”
  5. Avoid ALL CAPS and excessive punctuation (!!!, ???): Using all caps or excessive punctuation can make your email appear spammy or aggressive, increasing the likelihood of being flagged by spam filters. Instead, opt for a more natural writing style, like these examples:
    • “New eBook: Master the Art of Negotiation”
    • “Don’t Miss Our Exclusive Networking Event”
  6. Don’t use spam trigger words (Free, Offer, Limited Time, etc.): Certain words and phrases are commonly associated with spam, and using them in your subject lines may cause your email to be flagged by spam filters. To avoid this, refrain from using words like “Free,” “Offer,” “Limited Time,” “Act Now,” and “Guarantee.” Instead, focus on crafting subject lines that convey the value of your content without relying on these trigger words. For example:
    • “Discover the Benefits of Our Premium Membership”
    • “Save Big with Our Seasonal Sale – Ends Soon!”

By following these guidelines and examples, you can create compelling subject lines that entice recipients to open your emails while minimizing the risk of being caught by spam filters. Remember that the key to successful email subject lines, is to accurately represent your email content while sparking interest and engagement from your recipients. Keep in mind that the ideal subject line can vary depending on your audience and the nature of your email campaign. Regularly testing and analyzing the performance of different subject lines can help you better understand what resonates with your subscribers and improve your email open rates.

In addition, consider using A/B testing to optimize your subject lines further. A/B testing involves sending two different subject lines to a small portion of your email list and then analyzing which one performs better in terms of open rates, click-through rates, or other metrics. Once you have identified the winning subject line, send the email with that subject line to the rest of your list. This data-driven approach can help you refine your subject lines over time and continuously improve your email performance.

Authenticate Your Emails with DKIM, SPF, and DMARC

Authentication protocols like DKIM, SPF, and DMARC help email providers verify that your emails are legitimate, increasing their chances of passing spam filters. According to a study by Return Path, senders who use email authentication have an 83% higher email deliverability at rate than those who don’t. To set up these authentication methods, consult your ESP’s documentation or contact their support team for assistance.

Maintain a Clean Email List

As marketing guru Ann Handley emphasizes, “Quality is more important than quantity when it comes to your email list. Focus on building relationships with engaged subscribers, rather than just adding numbers.”

A clean email list is essential for ensuring your emails pass spam filters and reach engaged recipients. Maintaining a clean list helps improve deliverability, avoid spam filters reduce bounce rates, and protect your sender reputation. Here are some best practices and examples for maintaining a clean email list:

  1. Remove invalid, non-existent, or bounced email addresses: Email addresses that bounce or are invalid can harm your sender reputation and deliverability. To clean your list, use an email validation service, such as ZeroBounce, BriteVerify, or NeverBounce, to identify and remove invalid or non-existent addresses. Additionally, monitor your bounce rates and remove hard-bounced addresses promptly.
  2. Implement a double opt-in process to confirm subscribers’ intent to join your list: A double opt-in process requires new subscribers to confirm their subscription by clicking a link in a confirmation email. This approach ensures that only genuinely interested recipients join your list and helps prevent spam traps or fake email addresses from being added. For example, when a user subscribes to your newsletter on your website, they receive an email with a subject line like “Please Confirm Your Subscription to [Your Company] Newsletter.” The email contains a message like, “To complete your subscription, please click the link below to confirm your email address.”
  3. Regularly update and remove inactive subscribers: Inactive subscribers can negatively impact your email engagement rates and sender reputation. Develop a re-engagement campaign to identify and re-engage inactive subscribers. For example, send an email with a subject line like, “We Miss You! Here’s a Special Offer Just for You,” along with an incentive to re-engage, such as a discount or exclusive content.If the re-engagement campaign doesn’t yield results, consider removing these inactive subscribers from your list. You could also segment your list and send tailored content to the inactive subscribers to test whether specific topics or formats can rekindle their interest.
  4. Use a preference center to let subscribers customize their email experience: Allowing subscribers to manage their email preferences can help ensure that they receive only the content that interests them, reducing the likelihood of disengagement or unsubscribing. For example, provide options for subscribers to select their preferred email frequency or choose specific topics they wish to receive updates on.
  5. Monitor your email engagement metrics and act on the insights: Keep track of your open rates, click-through rates, and other key email metrics to identify trends and areas for improvement. Analyzing these metrics can help you identify segments of your list that are more or less engaged, allowing you to adjust your strategy accordingly.

Personalize Your Emails

Personalized emails are more likely to pass spam filters and engage your recipients. A study by Experian found that personalized emails deliver six times higher transaction rates. To personalize your emails:

  • Use the recipient’s name in the subject line or email body
  • Segment your list based on demographics or interests
  • Tailor content to the specific needs of each segment

Limit the Use of Images and External Links

Spam filters often flag emails containing excessive images or external links. To avoid spam do this:

  • Limit the number of images and external links in your emails
  • Opt for plain text or HTML emails instead of image-heavy designs
  • Ensure all external links lead to reputable and relevant websites

Comply with CAN-SPAM and GDPR Regulations

Compliance with email marketing regulations, such as CAN-SPAM and GDPR, not only helps your emails pass spam filters but also protects your business from spam complaints and potential legal issues. To ensure compliance:

  • Include a clear and visible unsubscribe link in every email
  • Provide a physical mailing address for your business
  • Don’t use deceptive subject lines or “From” addresses
  • Obtain proper consent from subscribers, particularly for those located in the EU

Test Your Emails with Spam Checkers

Before sending your emails, test them using spam checker tools to identify potential issues that could trigger spam filters. Some popular email spam filter checker tools include:

As author and digital marketing expert Jay Baer notes, “Taking the time to test and optimize your emails is a small investment that can yield big results.”

Monitor Your Sender Reputation

Your sender reputation is a crucial factor in whether your emails pass spam filters. To maintain a good sender reputation:

  • Avoid sending emails to non-existent or invalid addresses
  • Keep your complaint rate low by only emailing engaged subscribers
  • Check your sender reputation using tools like SenderScore or Google Postmaster Tools

According to a study by Return Path, senders with a high sender reputation score have a 95% deliverability rate, while those with a low score have only a 68% deliverability rate. If you’re looking to stop your emails from ending up in spam, click to learn our comprehensive guide to master email deliverability.

Send Consistent and Valuable Content

Consistently sending valuable content in email campaigns not only helps you build trust with your subscribers but also reduces the likelihood of your emails being marked as spam. To achieve this:

  • Send emails on a regular schedule
  • Focus on providing content that is relevant and valuable to your audience
  • Encourage engagement by asking for feedback and including calls to action

Frequently Asked Questions:

Q: How do spam filters work?

  • A: Spam filters use a combination of algorithms, machine learning, and user-generated data to determine the likelihood that an email is spam. Emails that exceed a certain spam score are flagged and redirected to the spam folder.

Q: Can I guarantee that my emails will pass spam filters?

  • A: While following the 10 tips for crafting emails that will pass spam filters can significantly increase your chances of avoiding the spam folder, no method is 100% foolproof. Email providers constantly update their filtering criteria, so it’s essential to stay informed and adapt your email strategies accordingly.

Q: What should I do if my emails are consistently marked as spam?

  • A: If your emails are consistently being marked as spam, review and implement the 10 tips for crafting emails that will pass spam filters. Additionally, consider reaching out to your ESP for support and guidance, as they may be able to offer insights specific to your situation.


Navigating the world of spam filters can be challenging, but by following these 10 tips for crafting emails that will pass spam filters, you can significantly improve your chances of reaching your intended audience. By choosing a reputable ESP, crafting compelling subject lines, authenticating your emails, maintaining a clean email list, personalizing your content, limiting images and external links, complying with regulations, testing with your spam filter and checkers, monitoring your sender reputation, and sending consistent and valuable content, you can help ensure that your messages land in the right inboxes and successfully engage your recipients. As email marketing expert Chad White advises, “Success in email marketing comes from consistently delivering value and respecting your subscribers’ inboxes.”

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