How to diagnose email deliverability issues and prevent emails from going to spam?

Key findings

• Technical setup: Proper email authentication, including SPF, DKIM, and DMARC, is fundamental for verifying sender identity and preventing spoofing, significantly impacting deliverability.
• Sender reputation: This is a critical factor influenced by bounce rates, spam complaints, engagement, and blocklist listings. A poor reputation almost guarantees emails will land in spam or be rejected.
• Content quality: The actual content of your email (links, images, spammy keywords) can trigger filters even with perfect technical setup.
• List hygiene: Sending to unengaged subscribers, invalid addresses, or spam traps severely harms your sender reputation.
• ISP policies: Internet Service Providers (ISPs) like Gmail and Yahoo have specific, evolving requirements that senders must meet.

Key considerations

• Proactive monitoring: Regularly monitor your email performance metrics, such as open rates, click-through rates, bounce rates, and spam complaint rates.
• Leverage tools: Utilize services like Google Postmaster Tools and other deliverability testing tools to identify issues before they become critical.
• Audience engagement: Focus on sending relevant, valuable content to engaged subscribers to minimize complaints and maximize positive interactions.
• Consistent sending: Maintain a consistent sending volume and schedule, avoiding sudden spikes or drops that can trigger spam filters.
• Feedback loops: Sign up for ISP feedback loops to promptly remove users who mark your emails as spam.

Key opinions

• Internal vs. external delivery: Marketers frequently note that emails can deliver internally within an organization due to policy, but still land in spam for external recipients.
• Spam filtering isn't absolute: It is generally understood that providers like Google won't send 100% of emails to spam unless the sender has an extremely poor reputation.
• Value of postmaster tools: Many marketers highly recommend setting up and actively using Google Postmaster Tools for diagnosing issues.
• Content and reputation: Focusing on subscriber relationships and maintaining a clean list are seen as crucial for avoiding the spam folder.

Key considerations

• Data collection: Collecting deliverability data over at least seven days from tools like Postmaster Tools can provide a clearer picture of trends and issues.
• Fundamental checks: Always verify basic technical configurations, such as email authentication (SPF, DKIM, DMARC), and assess the health of your sending IPs.
• List health monitoring: Continuously monitor bounce rates and complaint rates, and actively remove inactive or invalid email addresses to protect sender reputation.
• Proactive issue resolution: Utilize spam checkers and deliverability testing tools to proactively identify and resolve potential issues before they impact a wider audience.
• Engagement focus: Prioritize sending emails to engaged users who genuinely want to receive your messages to minimize spam complaints and maintain a positive sender score, as highlighted by Salesforce.

Key opinions

• IP reputation management: Experts consistently emphasize that diligent management of IP reputation is paramount for consistent inbox placement.
• Authentication is non-negotiable: Weak or improperly configured SPF, DKIM, and DMARC are often cited as primary reasons for emails being flagged or rejected by filters.
• Content and infrastructure interplay: Even with perfect infrastructure, poor content can lead to deliverability issues, while good content can sometimes compensate for minor technical imperfections.
• Proactive monitoring: The use of various postmaster tools and consistent data analysis is crucial for identifying and mitigating issues promptly.

Key considerations

• Audience segmentation: Improving inbox placement often involves strategic audience segmentation and sending priority.
• Blocklist impact: Understanding how blocklists (or blacklists) function and their impact on deliverability is essential for troubleshooting and removal processes.
• Mixed email types: Avoid mixing transactional and marketing emails from the same IP or domain, as this can negatively impact the deliverability of critical transactional messages.
• ISP-specific nuances: Pay close attention to specific requirements and filtering behaviors of major ISPs like Gmail and Yahoo, as they often have unique nuances.
• Feedback loops: Proactively engaging with ISP feedback loops helps remove complaining users from your list quickly, safeguarding your reputation.

Key findings

• Authentication standards: RFCs and official guides confirm SPF, DKIM, and DMARC as critical for email validation and preventing fraudulent mail.
• Sender reputation metrics: Tools like Google Postmaster provide sender reputation data based on spam rates, IP reputation, and domain reputation, which are direct indicators of deliverability.
• List hygiene importance: Documentation frequently stresses the need to clean email lists, remove inactive subscribers, and avoid spam traps to maintain good sender health.
• Content guidelines: Many providers offer explicit guidelines on email content to avoid spam triggers, including link types, image usage, and keyword avoidance.

Key considerations

• DMARC policy implementation: Safely transitioning your DMARC policy to quarantine or reject requires careful monitoring of reports and a phased approach.
• Engagement signals: ISPs increasingly rely on user engagement (opens, clicks, replies) as a primary signal for inbox placement, as outlined in their filtering documentation.
• Compliance with new requirements: Staying updated with evolving requirements from providers like Gmail and Yahoo (e.g., one-click unsubscribe, lower spam rates) is critical to maintaining good standing.
• Consistent sending patterns: Gradual warm-up of new IPs and domains, along with consistent sending volumes, are frequently recommended to build and maintain reputation.
• Domain reputation: A practical guide to understanding your email domain reputation is often provided, emphasizing its long-term impact on deliverability.