What is an email deliverability audit?

An email deliverability audit is a systematic review of all factors affecting whether your emails reach the inbox, including authentication records (SPF, DKIM, DMARC), sender reputation, list hygiene, content quality, and sending infrastructure.

How often should I conduct an email deliverability audit?

A comprehensive audit should be conducted quarterly at minimum, with continuous monitoring of key metrics like bounce rates, complaint rates, and blocklist status in between full audits.

What are the most common email deliverability issues?

The most common issues include misconfigured authentication records (SPF/DKIM/DMARC misalignment), poor list hygiene leading to spam trap hits, high complaint rates above 0.1%, IP or domain blocklisting, and missing List-Unsubscribe headers.

How do I check my sender reputation?

Check sender reputation using Google Postmaster Tools for Gmail, Microsoft SNDS for Outlook, and third-party services like Sender Score. Also verify your IPs and domains are not listed on DNS-based blocklists like Spamhaus or Barracuda.

What bounce rate is acceptable for email?

Hard bounce rates should stay below 2%. Anything consistently above that threshold signals list quality problems such as outdated addresses, invalid entries, or insufficient list validation processes.

Email Deliverability Audit — What to Check

Your emails are sending. But are they arriving?

An email deliverability audit answers that question definitively. It’s the systematic review of every factor that determines whether your messages reach the inbox, land in spam, or disappear entirely. Whether you’re troubleshooting a sudden drop in engagement or proactively protecting sender reputation, here’s what to check.

1. Authentication Records

Start at the DNS layer. Verify that your SPF, DKIM, and DMARC records are correctly configured, aligned, and passing validation:

SPF — Confirm your record includes every IP and service authorized to send on your behalf. Watch for the 10-lookup limit.
DKIM — Validate that signing keys are active, properly rotated, and that the d= domain aligns with your From header.
DMARC — Check your policy (none, quarantine, or reject) and review aggregate reports for authentication failures you didn’t expect.

2. Sender Reputation

Your IP and domain reputation directly influence inbox placement. During an audit, check:

IP reputation via Google Postmaster Tools, Microsoft SNDS, and third-party reputation services
Domain reputation across major mailbox providers
Presence on any DNS-based blocklists (Spamhaus, Barracuda, SORBS)
Bounce rates — anything above 2% signals list quality issues

3. List Hygiene

Dead addresses, spam traps, and disengaged recipients erode your reputation over time. Audit for:

Hard bounce rate trends
Complaint (FBL) rates — stay below 0.1%
Spam trap hits indicating aged or purchased lists
Engagement segmentation — are you still mailing recipients who haven’t opened in 12+ months?

4. Content & Infrastructure

Even with perfect authentication and a clean list, content and infrastructure issues can trigger filtering:

Check for spam-trigger patterns in subject lines and body copy
Verify proper MIME structure (text/plain + text/html multipart)
Confirm working unsubscribe links and List-Unsubscribe headers
Review sending infrastructure — dedicated vs. shared IPs, proper rDNS, TLS enforcement
Test inbox placement across Gmail, Outlook, Yahoo, and Apple Mail

5. Monitoring & Reporting

A one-time audit is valuable. Continuous monitoring is essential. Set up:

DMARC aggregate and forensic report processing
Automated blocklist monitoring
Inbox placement testing on a regular cadence
Engagement metric dashboards tracking opens, clicks, bounces, and complaints by sending domain

The Bottom Line

Email deliverability isn’t a set-it-and-forget-it configuration. It’s an ongoing discipline. A thorough audit covers authentication, reputation, list quality, content, and infrastructure — and each layer depends on the others. One misconfigured SPF record or a spike in complaints can cascade into inbox placement problems across your entire sending program.

Run the audit. Fix what’s broken. Monitor what’s working. Your messages deserve to be read.

Need help evaluating your current email infrastructure? Explore our comparison tools to find the right delivery platform for your needs.

Author

Harry Shuford

Harry Shuford is an IT specialist and technical writer with a focus on email delivery, deliverability, and the systems that power modern digital communication. With a strong understanding of the technical factors that influence email performance, he writes blog content that helps businesses better understand inbox placement, infrastructure, and best practices for reliable email delivery.