Definition
A deliverability audit is a comprehensive review of all factors affecting whether your emails reach the inbox rather than the spam folder. It covers technical infrastructure (authentication, DNS, IP reputation), sending practices (volume, frequency, list quality), and content quality (engagement, complaints, spam traps).
Regular deliverability audits help identify problems before they significantly impact inbox placement rates. They are essential after ESP migration, after a deliverability incident, or on an ongoing quarterly basis.
Audit Checklist
Technical Infrastructure
| Check | What to Verify |
|---|---|
| SPF record | Includes all legitimate sending IPs |
| DKIM signing | Enabled and properly configured |
| DMARC policy | Set to at least p=quarantine or p=reject |
| Reverse DNS | Matches your sending domain |
| MX records | Point to your mail servers |
| List-Unsubscribe header | Properly configured |
| Feedback loop | Registered with major ISPs |
Sending Practices
- Volume ramp-up plan in place for new IPs
- Consistent send schedule (not bursty)
- Bounce handling within 24-48 hours
- Complaint rate under 0.1%
- Spam trap count at zero or near zero
- Unknown user rate under 2-3%
Content and Engagement
- Spam score under 5 (using tools like SpamAssassin)
- Text-to-image ratio balanced (60:40 minimum)
- Low number of spam trigger words
- Active engagement monitoring programme
- Sunset policy for inactive subscribers
- Relevant subject lines matching email content
Audit Process
- Pre-audit data collection: Gather sending data, authentication records, engagement metrics
- Infrastructure review: Check DNS, authentication, IP reputation
- Content analysis: Review recent campaigns for spam score and quality
- List assessment: Analyse list health, bounce rates, spam trap hits
- Engagement analysis: Review open, click, and complaint trends
- Report and recommendations: Document findings and prioritised action items
- Implementation: Make technical and process changes
- Follow-up audit: Verify improvements 30-60 days later
Related Glossary Terms
AOL Mail for Email Marketers
AOL Mail is a legacy email provider with specific deliverability requirements and rendering quirks, now operating as part of the Yahoo+AOL network under shared infrastructure.
BIMI
BIMI (Brand Indicators for Message Identification) is an email standard that allows brands to display their logo next to their emails in supported email clients. It requires DMARC enforcement at quarantine or reject policy.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.
Email Deliverability
Email deliverability is the ability to land in the recipient's inbox rather than the spam folder. It depends on sender reputation, authentication, list quality, and content practices.
DKIM (DomainKeys Identified Mail)
DKIM (DomainKeys Identified Mail) is an email authentication method that uses digital signatures to verify that an email was not tampered with during transit and comes from a authorised domain.
DMARC (Domain-based Message Authentication)
DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email authentication protocol that builds on SPF and DKIM to prevent domain spoofing and provide reporting on authentication failures.
Frequently Asked Questions
Conduct a full audit quarterly. Perform a focused check (authentication, complaint rate, spam trap hits) monthly. Run a comprehensive audit immediately if you experience a sudden drop in open rates or a spike in spam complaints.
A standard audit takes 1-3 days for an internal team or 1-2 weeks with an external consultant. The timeline depends on the complexity of your email programme and the depth of analysis needed.
Authentication configuration errors are the most common technical issue found in audits — particularly missing or incorrect SPF records and DKIM not properly enabled. List hygiene (high bounce rates, spam traps, unengaged subscribers) is the most common practice issue.