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Causes of Low Email Deliverability and How to Improve It

Published 6/26/2024

Email marketing remains a cornerstone of digital communication, but achieving high deliverability rates can be challenging. Understanding the factors influencing email deliverability and implementing effective strategies to enhance it are crucial for successful campaigns. In this comprehensive guide, we delve into the causes of low email deliverability and provide actionable tips to optimize your email marketing efforts.

Understanding Email Deliverability

Email deliverability refers to the ability of your emails to reach recipients' inboxes successfully. A high deliverability rate ensures that your messages are not flagged as spam and are actually seen by your intended audience. Several factors influence email deliverability, and addressing these proactively can significantly improve your campaign's effectiveness.

Common Causes of Low Email Deliverability

  1. Poor Sender Reputation:

    • Cause: Sending emails from domains or IPs with a history of spam complaints or low engagement rates.
    • Improvement: Build and maintain a positive sender reputation by sending relevant content to engaged subscribers. Monitor your sender score using tools like SenderScore.org or Return Path.
  2. Incorrect Authentication:

    • Cause: Missing or misconfigured authentication records like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance).
    • Improvement: Ensure all authentication protocols are properly set up and authenticated. Use tools like SPF/DKIM record checkers to verify configurations.
  3. Poor List Hygiene:

    • Cause: Sending emails to outdated, inactive, or purchased email lists can increase bounce rates and trigger spam filters.
    • Improvement: Regularly clean your email lists by removing inactive subscribers and unsubscribes. Implement double opt-in processes to ensure list quality.
  4. Spam Triggers in Content:

    • Cause: Using spammy content such as excessive use of exclamation marks, misleading subject lines, or triggering spam filters.
    • Improvement: Craft clear and relevant subject lines and email content. Use spam checkers like SpamAssassin or Mail Tester to analyze and optimize your email content.
  5. High Complaint Rates:

    • Cause: Recipients marking your emails as spam due to irrelevant or unsolicited content.
    • Improvement: Segment your audience and send targeted, personalized content. Encourage subscribers to whitelist your email address and provide clear unsubscribe options.
  6. Technical Issues with Email Servers:

    • Cause: Server downtime, configuration errors, or sending too many emails simultaneously.
    • Improvement: Monitor server performance and ensure optimal email sending practices. Use email service providers (ESPs) with reliable infrastructure and support.
  7. Lack of Engagement:

    • Cause: Low open rates, click-through rates, or engagement metrics indicate disinterest from subscribers.
    • Improvement: Segment your lists based on engagement levels. Send relevant and valuable content to re-engage inactive subscribers. Use A/B testing to optimize subject lines and email content.

Strategies to Improve Email Deliverability

  1. Maintain a Clean Email List: Regularly remove inactive subscribers and manage bounce rates to improve list hygiene.

  2. Authenticate Your Domain: Implement SPF, DKIM, and DMARC protocols to verify your identity and reduce the likelihood of emails being marked as spam.

  3. Monitor Sender Reputation: Use tools to monitor your sender score and reputation metrics. Address issues promptly to maintain a positive reputation.

  4. Optimize Email Content: Craft compelling subject lines and relevant content that resonates with your audience. Avoid spam triggers and maintain transparency.

  5. Engage Subscribers: Segment your audience and personalize content to increase engagement. Encourage interaction and feedback from subscribers.

  6. Monitor and Test: Continuously monitor email performance metrics and conduct A/B testing to optimize deliverability and campaign effectiveness.


Achieving high email deliverability requires a proactive approach to managing sender reputation, list hygiene, authentication protocols, and content quality. By addressing the causes of low deliverability and implementing these strategies, businesses can maximize the impact of their email marketing efforts, reach more subscribers, and drive meaningful engagement.