How to diagnose and improve email deliverability and open rates?

Key findings

• Sudden drop in open rates: A significant decline in open rates for a large campaign, especially when similar campaigns performed well, strongly suggests a deliverability problem, not just poor subject line performance. This could mean emails are not reaching the inbox at all.
• Content matters: Even seemingly innocuous words, like "flash sale" in a business-to-business context, can trigger spam filters if they do not align with subscriber expectations or industry norms, causing emails to land in spam.
• ISP-specific issues: Problems may be localized to specific internet service providers (ISPs), such as Gmail, especially if they represent a large segment of your audience. Tools like Google Postmaster Tools are essential for diagnosing these issues.
• External content: The use of third-party tools for elements like animated countdown timers can introduce new deliverability variables, even if the primary sending infrastructure remains unchanged.

Key considerations

• Utilize diagnostic tools: Use tools like Google's Message Header analyzer to check for email delays or specific routing issues. More importantly, establish and monitor your domain's performance using Google Postmaster Tools for day-to-day reputation insights.
• Assess ESP reporting: Verify if your ESP (e.g., Marketo) provides granular data, such as open rates broken down by ISP. This can pinpoint where deliverability issues are most acute.
• Review subject lines and content: Continuously test and refine your subject lines and email content, ensuring they align with your brand, audience expectations, and industry best practices to avoid triggering spam filters. A helpful resource is Shopify's guide on email deliverability.
• Proactive monitoring: Do not wait for a major drop in open rates to troubleshoot. Implement ongoing email deliverability monitoring practices.

Key opinions

• Immediate analysis: Many marketers immediately question if low open rates are due to Gmail quarantining or delaying inbox placement, particularly for large campaigns.
• Self-diagnosis limitations: Without dedicated inbox placement tools, marketers often resort to personal testing, like checking if they received the email when expected, or considering issues like reporting delays or poor subject lines.
• ESP role: Some marketers suggest that the ESP itself might be rate-limiting campaigns to prevent deferrals, especially if the campaign size is significantly larger than usual.
• Content impact: There is a strong consensus that specific content, such as certain promotional phrases in subject lines, can cause emails to land in the spam folder, particularly for B2B audiences.
• Third-party elements: The introduction of new third-party tools or elements within an email, like animated timers, is recognized as a potential factor affecting deliverability.

Key considerations

• Check ISP-specific issues: Prioritize checking deliverability and open rates across different ISPs, not just the largest one (e.g., Gmail), to see if the issue is widespread or isolated. This directly influences how to improve low Gmail email open rates.
• Leverage available ESP data: Even without advanced tools, marketers should explore whether their current ESP provides any breakdown of open rates by ISP or domain, as this data can be highly indicative.
• Content and audience alignment: Review subject lines and body content for phrases that might be misinterpreted or flagged by spam filters, especially when targeting a professional (B2B) audience. Higher Logic offers insights into email deliverability metrics.
• Monitor ESP performance: If a drastic drop in open rates occurs, consider reaching out to the ESP to inquire about any system problems or intentional rate limiting that might be affecting delivery.

Key opinions

• Holistic view: Experts believe that a drop in open rates is rarely due to a single factor but often a combination of sender reputation, content relevance, and list quality issues.
• Reputation is key: Maintaining a good sender reputation is paramount, as ISPs heavily rely on it to decide inbox placement. This includes both IP and domain reputation.
• Engagement signals: Positive engagement (opens, clicks, replies) and low negative feedback (complaints, unsubscribes, bounces) are crucial for long-term deliverability.
• List hygiene: Regularly cleaning email lists to remove inactive or invalid addresses prevents hard bounces and spam trap hits, which significantly harm sender reputation.
• Content relevance: Sending content that is highly relevant and personalized to the subscriber's interests boosts engagement and reduces spam complaints.

Key considerations

• Monitor domain reputation: Actively use tools like Google Postmaster Tools to track your domain and IP reputation with major ISPs. This offers critical insights into how your mail is perceived. You can learn more in our ultimate guide to Google Postmaster Tools domain reputation.
• Implement authentication: Ensure proper SPF, DKIM, and DMARC authentication is set up and aligned, as these are fundamental for proving sender legitimacy. Our simple guide to DMARC, SPF, and DKIM can help.
• Content optimization: Beyond spam triggers, ensure content provides value, is personalized, and has clear calls to action to drive positive engagement. CleverTap provides tips on writing compelling subject lines.
• Consistent sending patterns: Maintain consistent sending volume and frequency to build and sustain a reliable sender reputation with ISPs.

Key findings

• Authentication is foundational: Proper configuration of SPF, DKIM, and DMARC records is crucial for email authentication and verifying sender identity, which directly impacts inbox placement.
• Sender reputation metrics: ISPs (like Gmail) use sophisticated reputation systems based on various signals (spam complaints, user engagement, sending volume) to classify incoming mail.
• Content and context: Email content, including subject lines, is analyzed for spam characteristics and relevance to the recipient, affecting whether it lands in the inbox or spam folder.
• Engagement feedback: Positive user engagement (e.g., opens, replies, adding to contacts) signals to ISPs that the mail is desired, while negative engagement (e.g., marking as spam) damages sender reputation.
• List quality: High bounce rates and hits on spam traps indicate poor list hygiene, which severely degrades sender reputation and deliverability.

Key considerations

• Regularly check authentication: Periodically verify your SPF, DKIM, and DMARC records to ensure they are correctly configured and aligned. Use a free online email testing tool to check your records.
• Monitor sender reputation dashboards: Utilize ISP-specific tools, like Google Postmaster Tools, to gain insights into your domain's and IP's performance metrics directly from the source. Also look for blocklist monitoring tools.
• Segment and personalize: Sending relevant content to engaged segments of your audience will naturally improve engagement metrics and sender reputation, minimizing spam complaints.
• Maintain list hygiene: Regularly clean your email list of unengaged subscribers and invalid addresses to reduce bounce rates and avoid spam traps. This also improves the overall health of your email list.