Email Deliverability Audit Checklist: 28 Essential Steps to Reach the Inbox
Email deliverability determines whether your carefully crafted messages reach your audience’s inbox or disappear into spam folders. An email deliverability audit examines every technical, content, and strategic element that influences how inbox providers treat your emails. From authentication protocols to sender reputation, each factor plays a critical role in ensuring your messages get delivered, opened, and acted upon.
Whether you’re a marketing manager struggling with declining open rates, a business owner launching a new email campaign, or an email specialist optimizing performance, this checklist provides a systematic approach to diagnosing and fixing deliverability issues. Use this guide to work through each category methodically, checking off items as you complete them. By addressing these 28 critical elements, you’ll build a foundation for consistent inbox placement and stronger email marketing results.
Email Authentication (5 Items)
Ensure emails are verified and trusted by ISPs to improve deliverability and prevent spoofing.
Set Up SPF, DKIM, and DMARC Records
Implement these authentication protocols to verify your emails’ legitimacy, reducing the risk of spoofing and improving deliverability. SPF authorizes which servers can send email from your domain, DKIM adds a digital signature to verify message integrity, and DMARC tells receiving servers how to handle authentication failures. Together, these protocols create a trust framework that inbox providers use to determine whether your emails deserve inbox placement.
Verify SPF Record Validity
Ensure your SPF record is correctly configured to include all sending IPs, preventing unauthorized use of your domain. An SPF record should list every mail server and third-party service authorized to send on your behalf, including your ESP, CRM, and any other email tools. Test your SPF record using validation tools to confirm it doesn’t exceed the 10 DNS lookup limit, which can cause authentication failures.
Verify DKIM Record Validity
Check that your DKIM signature is valid to authenticate your emails and ensure they haven’t been altered. Your email service provider typically generates DKIM keys, but you’re responsible for publishing the public key in your DNS records. Use DKIM validators to confirm the signature passes authentication checks, and rotate keys annually to maintain security standards.
Publish DMARC Record
Implement a DMARC policy to protect your domain from unauthorized use and improve email deliverability. Start with a monitoring policy (p=none) to collect data about who’s sending emails from your domain, then gradually move to quarantine or reject policies as you gain confidence. DMARC alignment requires either SPF or DKIM to pass and align with your from domain, creating a powerful authentication framework.
Monitor Authentication Results
Regularly check SPF, DKIM, and DMARC results to ensure they are passing and aligned. Review DMARC aggregate reports weekly to identify authentication failures, unauthorized senders, or configuration issues. Most email service providers offer dashboards showing authentication pass rates, but you can also use third-party tools to analyze DMARC XML reports and spot trends that need attention.
Sender Reputation Management (4 Items)
Maintain a positive sender reputation to ensure emails reach the inbox.
Monitor Sender Reputation
Use tools like Google Postmaster to track domain and IP reputation, addressing issues promptly. Sender reputation scores range from low to high, with inbox providers using these scores to determine inbox placement. Check your reputation weekly across multiple providers, watching for sudden drops that indicate deliverability problems requiring immediate investigation.
Check Domain Blacklist Status
Regularly verify that your domain is not listed on blacklists to avoid deliverability issues. Major blacklists like Spamhaus, SURBL, and Barracuda can severely impact inbox placement when your domain appears on them. Use blacklist monitoring tools to check your status across dozens of lists simultaneously, and if listed, follow each blacklist’s specific removal process while addressing the underlying issue.
Maintain Low Spam Complaint Rate
Keep spam complaint rates under 0.1% to protect your sender reputation. When recipients mark your emails as spam, inbox providers interpret this as a strong signal that your content isn’t wanted. Monitor complaint rates through your ESP’s feedback loop reports, and investigate spikes immediately by reviewing the content, targeting, and frequency of campaigns that generated complaints.
Monitor Bounce Rates
Ensure bounce rates are under 2% to maintain a healthy sender reputation. Hard bounces indicate invalid or non-existent email addresses, while soft bounces suggest temporary issues like full mailboxes. Remove hard bounces immediately from your list, and suppress addresses that soft bounce repeatedly. High bounce rates signal poor list hygiene and can damage your reputation with inbox providers.
Email Content and Design (4 Items)
Craft emails that engage recipients and avoid spam filters.
Avoid Spam Trigger Words
Steer clear of words like ‘FREE’ and ‘GUARANTEED’ to prevent triggering spam filters. While no single word automatically sends emails to spam, certain phrases raise red flags when combined with other suspicious signals. Focus on authentic, value-driven language rather than hype-filled promises, and test your subject lines and content through spam filter checkers before sending.
Maintain Balanced Text-to-Image Ratio
Ensure a balanced ratio to avoid spam filters and ensure accessibility. Emails consisting entirely of images raise spam filter suspicions because spammers historically used this tactic to evade text-based filters. Aim for at least 60% text content, include alt text for all images, and ensure your message makes sense even if images don’t load.
Include Proper Unsubscribe Mechanism
Provide a clear unsubscribe option to comply with regulations and reduce complaints. The unsubscribe link should be easy to find, typically in the footer, and process requests immediately without requiring login or additional steps. Making it difficult to unsubscribe frustrates recipients and increases spam complaints, which damage your reputation far more than losing a subscriber.
Ensure Mobile Responsive Design
Design emails to be responsive across devices to enhance user experience. Over 60% of emails are opened on mobile devices, so your layout must adapt to smaller screens with readable text, tappable buttons, and properly scaled images. Test emails on multiple devices and email clients before sending, paying special attention to how Gmail and Apple Mail render your design.
Email List Management (4 Items)
Maintain a clean and engaged email list to improve deliverability.
Regularly Clean Your Email List
Remove outdated or invalid addresses to prevent high bounce rates. Email addresses decay at roughly 22% per year as people change jobs, abandon accounts, or switch providers. Run your list through an email verification service quarterly to identify invalid addresses, spam traps, and temporary domains before they damage your sender reputation.
Use Double Opt-In for New Subscribers
Confirm subscribers’ interest to reduce fake addresses and improve engagement. Double opt-in requires new subscribers to click a confirmation link before joining your list, ensuring they provided a valid address and genuinely want your emails. While this adds friction to the signup process, it dramatically improves list quality and protects against spam trap addresses.
Segment Your Email List
Target emails based on engagement to maintain high engagement rates. Sending the same message to your entire list ignores differences in interests, behavior, and engagement levels. Create segments based on purchase history, email opens, website activity, and demographic data to send more relevant content that drives higher open and click rates.
Implement a Sunset Policy for Inactive Subscribers
Suppress inactive subscribers to maintain list hygiene and improve engagement rates. Subscribers who haven’t opened or clicked your emails in 6-12 months drag down your engagement metrics and can damage your sender reputation. Send a re-engagement campaign to win them back, then remove those who remain unresponsive to focus on your active, interested audience.
Sending Practices (3 Items)
Adopt best practices for sending emails to maintain a positive sender reputation.
Warm Up New Accounts Gradually
Increase sending volume over weeks to build a positive reputation. When you start sending from a new IP address or domain, inbox providers have no history to evaluate your trustworthiness. Begin by sending to your most engaged subscribers, gradually increasing volume by 20-30% daily over 4-6 weeks until you reach your target sending volume.
Monitor Sending Volume
Keep email volume under control to avoid being flagged as spam. Sudden spikes in sending volume trigger spam filters because this pattern resembles compromised accounts or spammers ramping up operations. Maintain consistent sending patterns, and if you need to increase volume for a campaign, do so gradually while monitoring engagement metrics closely.
Separate Transactional and Marketing Emails
Use different infrastructures to prevent marketing emails from affecting transactional deliverability. Transactional emails like password resets and order confirmations have higher engagement rates and stricter delivery requirements than promotional content. Sending them from separate domains or IP addresses protects critical transactional messages if marketing campaigns encounter deliverability issues.
Compliance and Legal (2 Items)
Ensure compliance with email marketing regulations to avoid penalties and maintain trust.
Ensure Compliance with CAN-SPAM and GDPR
Include unsubscribe options and avoid misleading subject lines to comply with regulations. CAN-SPAM requires accurate header information, clear identification as an advertisement, and a working unsubscribe mechanism. GDPR adds requirements for explicit consent, data processing transparency, and the right to erasure. Non-compliance can result in fines up to $43,792 per violation under CAN-SPAM or 4% of annual revenue under GDPR.
Include Physical Postal Address in Email Footer
A legal requirement that helps build trust with recipients. CAN-SPAM mandates including your valid physical postal address in every commercial email. This can be your business address, a registered P.O. box, or a private mailbox registered with a commercial mail receiving agency. The address demonstrates legitimacy and gives recipients confidence in your business.
Monitoring and Analytics (3 Items)
Regularly track and analyze email performance to identify and resolve deliverability issues.
Monitor Your Email Deliverability Rates
Track deliverability rates to ensure emails reach inboxes and identify potential issues early. Deliverability rate measures the percentage of emails that successfully reach recipient inboxes rather than bouncing or landing in spam folders. Aim for deliverability rates above 95%, and investigate immediately when rates drop below this threshold to identify authentication problems, reputation issues, or content concerns.
Conduct Regular Deliverability Audits
Regular audits help maintain high deliverability and quickly address emerging issues. Schedule comprehensive email deliverability audits quarterly to review authentication settings, sender reputation, list quality, content practices, and compliance. These audits catch problems before they escalate into serious deliverability crises and ensure you’re following current best practices as inbox provider algorithms evolve.
Use Spam Filter Testing Tools
Analyze how emails are treated by spam filters to make necessary adjustments. Tools like Mail Tester, GlockApps, and Litmus Spam Testing show how major inbox providers score your emails before you send them to your entire list. Test each campaign to identify content, authentication, or technical issues that might trigger spam filters, then make adjustments to improve inbox placement.
Technical Setup (3 Items)
Ensure your technical infrastructure supports high deliverability and compliance.
Configure Reverse DNS
Helps ISPs verify your sending domain, improving deliverability. Reverse DNS (rDNS or PTR record) maps your sending IP address back to your domain name, confirming that your IP address is associated with a legitimate domain. Many inbox providers check for matching forward and reverse DNS as part of their authentication process, and missing rDNS can trigger spam filters.
Set Up Custom Tracking Domain
Avoids common blacklists and maintains brand consistency. When you use your ESP’s default tracking domain for click and open tracking, you share reputation with all their other customers. A custom tracking domain (like track.yourdomain.com) gives you independent reputation control and prevents your emails from being affected by other senders’ poor practices.
Enable TLS Encryption
Ensures secure email transmission, enhancing trust with recipients. Transport Layer Security (TLS) encrypts email content as it travels between mail servers, protecting sensitive information from interception. Most modern email providers require TLS for email delivery, and enabling it demonstrates your commitment to security while improving deliverability with security-conscious inbox providers.
Completing this email deliverability audit positions your email program for consistent inbox placement and stronger engagement. Each item you’ve checked off addresses a specific factor that inbox providers evaluate when deciding whether to deliver your emails. From authentication protocols that verify your identity to content practices that engage recipients, these elements work together to build trust with both inbox providers and your audience.
Deliverability isn’t a one-time fix but an ongoing commitment to best practices, monitoring, and optimization. If you’re ready to take your email marketing to the next level with expert guidance on deliverability, strategy, and execution, we’re here to help. Let’s Talk Growth and explore how we can work together to ensure your messages reach the right people at the right time.
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