How to Run a Deliverability Audit for Your Agency Clients

Email deliverability is the backbone of every successful cold email campaign. For agencies managing multiple clients, ensuring high inbox placement and resolving technical issues is critical, not just for campaign results, but for long-term client trust and retention.
A deliverability audit is your blueprint for diagnosing and fixing the issues that keep your clients’ emails out of the inbox. Whether you’re working with startups or fast-moving sales teams, a thorough audit uncovers hidden problems, optimizes technical setup, and ensures your outreach lands where it matters most.
In this guide, you’ll learn how to run a complete deliverability audit for your agency clients, from technical checks to actionable recommendations, so you can boost performance, demonstrate results, and grow your agency’s reputation as a deliverability expert.

What Is Email Deliverability & Why Does It Matter?

Email deliverability refers to the ability of your emails to reach the recipient’s inbox, rather than the spam folder or bounce altogether. High deliverability means your emails are being seen, opened, and acted on by your target audience. Poor deliverability, on the other hand, can quietly sabotage even the best-written campaigns.

For agencies, deliverability is more than a technical metric; it’s a direct reflection of your value to clients. If your emails aren’t getting delivered, your clients aren’t seeing results. That’s why a deliverability audit is essential for any agency offering cold email or outreach services.

Key Components of a Deliverability Audit

A comprehensive deliverability audit covers several technical and strategic areas:

• Domain & DNS Configuration Check: Ensure domains are set up correctly, with proper DNS records (SPF, DKIM, DMARC) in place.

• Inbox & Mailbox Setup Review: Verify that inboxes are configured for optimal sending and receiving.

• Sender Reputation Analysis: Assess the reputation of sending domains and IPs.

• Content & Template Evaluation: Review email content for spam triggers, formatting issues, and personalization.

• Sending Volume & List Hygiene: Analyze sending patterns, list quality, and engagement rates.

• Authentication Protocols: Confirm SPF, DKIM, and DMARC are correctly implemented.

• Blacklist & Spam Trap Checks: Identify if domains or IPs are listed on blocklists or hitting spam traps.

• Performance Metrics Review: Examine open rates, bounce rates, and inbox placement statistics.

Step-by-Step: Running a Deliverability Audit

Step 1: Gather Technical Details

Before diving into analysis, collect all necessary information about your client’s email infrastructure. This includes:

• Domain names in use for sending

• DNS provider and access

• Email service providers (e.g., Google Workspace, Outlook)

• List of all sending IP addresses and mailboxes

Having this data upfront streamlines the audit and ensures no critical element is missed.

Step 2: Assess DNS and Authentication

Verify that essential DNS records are in place and correctly configured:

• SPF (Sender Policy Framework): Make sure the SPF record authorizes all legitimate sending sources.

• DKIM (DomainKeys Identified Mail): Ensure DKIM is set up and signing outbound emails.

• DMARC (Domain-based Message Authentication, Reporting & Conformance): Confirm a DMARC policy is published and monitored.

Check for typos, outdated records, or missing entries. Use online tools to validate DNS and authentication status.

Step 3: Evaluate Sender Reputation

Sender reputation is a major factor in inbox placement. To assess it:

• Check domain and IP reputation using tools like Google Postmaster Tools or Talos Intelligence.

• Look for recent blacklists or spam complaints.

• Review bounce rates and feedback loops.

If reputation is low, identify the root cause, such as spam complaints, high bounce rates, or a new domain/IP.

Step 4: Review Content and Templates

Audit email content for elements that might trigger spam filters:

• Overuse of salesy language or spammy keywords

• Lack of personalization or generic templates

• Excessive links or images

• Poor HTML formatting or missing text versions

Test emails with spam-checking tools, and recommend improvements based on best practices.

Step 5: Analyze Sending Patterns & Lists

Look at how emails are being sent and to whom:

• Sending volume (daily/weekly/monthly)

• Number of recipients per campaign

• List segmentation and targeting

• List hygiene (removal of inactive or invalid addresses)

Healthy sending patterns and clean lists reduce the risk of hitting spam traps and improve engagement.

Step 6: Monitor Placement & Engagement

Use inbox placement and engagement metrics to gauge real-world performance:

• Inbox vs. spam folder rates

• Open, click, and reply rates

• Deliverability by provider (Gmail, Outlook, Yahoo, etc.)

Compare these metrics to industry benchmarks and flag any significant deviations.

Step 7: Compile Findings & Recommendations

Summarize your findings in an actionable report:

• Highlight critical issues and quick wins

• Prioritize fixes based on impact

• Provide clear, step-by-step recommendations

Common Issues & How to Fix Them

Agencies often encounter recurring challenges during deliverability audits. Here are some of the most common, with solutions:

• Missing or Incorrect DNS Records: Double-check SPF, DKIM, and DMARC. Use DNS checkers to spot errors and update records as needed.
• Low Sender Reputation: Pause sending from problematic domains/IPs. Address root causes like spam complaints or poor list hygiene. Consider warming up new domains.
• Content Triggering Spam Filters: Simplify templates, avoid spammy language, and test before sending. Use plain text and personalize content.
• List Quality Issues: Regularly clean lists to remove bounces and inactive addresses. Use double opt-in where possible.
• High Bounce or Complaint Rates: Remove invalid addresses, segment lists, and monitor feedback loops for complaints.
• Blacklisting: Identify which list(s) you’re on, follow delisting procedures, and fix underlying issues before resuming full sending.

By proactively addressing these issues, you can dramatically improve inbox placement and campaign results.

Ongoing Monitoring & Optimization

A deliverability audit isn’t a one-time event; it’s the foundation for ongoing improvement. To ensure lasting results for your agency clients:

• Set up regular monitoring: Schedule monthly or quarterly check-ins to review key metrics and technical setup.

• Automate alerts: Use tools that notify you of authentication failures, blacklisting, or reputation drops.

• Continuously clean lists: Remove inactive or bounced addresses and encourage clients to segment their lists based on engagement.

• Test before every campaign: Run content through spam checkers and seedlist tests to catch issues early.

• Educate your clients: Provide best practices and training to help them maintain high deliverability between audits.

Proactive monitoring keeps your clients’ outreach healthy and maximizes ROI over time.

Conclusion

Running a thorough deliverability audit is one of the most impactful ways agencies can improve their clients’ cold email results. By following a structured process, covering technical setup, content, reputation, and ongoing monitoring, you’ll not only solve immediate issues but also empower your clients for long-term success.
Ready to take your agency’s deliverability to the next level? Book a demo with Mailpool and see how our platform can help you manage bulk email infrastructure, scale outreach, and achieve unbeatable inbox placement rates for every client.