Email Deliverability Scoring: Why Your Message Quality Matters
Beyond Authentication: The Full Deliverability Picture
SPF, DKIM, and DMARC are essential—but they're just the foundation. Email providers evaluate dozens of factors to decide whether your email reaches the inbox:
- **Authentication** (SPF, DKIM, DMARC alignment) - **Sender Reputation** (IP and domain history) - **Content Quality** (spam triggers, formatting) - **Engagement Signals** (opens, clicks, complaints) - **Technical Setup** (valid headers, proper formatting)
A deliverability score combines all these factors into a single metric that predicts whether your emails will be delivered.
Understanding Sender Reputation
Your sender reputation is like a credit score for email. It's built over time and affects every email you send.
**IP Reputation**: The history of emails sent from your sending IP addresses. Shared IPs (common in email service providers) can be risky if other senders abuse them.
**Domain Reputation**: The history associated with your sending domain. This follows you even if you change email providers.
Both Gmail and Microsoft maintain their own reputation systems, which is why the same email might land in the inbox for one recipient and spam for another.
Use Google Postmaster Tools and Microsoft SNDS to monitor your reputation with these major providers.
The Anatomy of a Deliverability Score
A comprehensive deliverability score evaluates:
- Authentication Score (30%) – SPF, DKIM, DMARC pass rates and alignment
- Infrastructure Score (20%) – PTR records, blacklist status, sending IP health
- Content Score (20%) – Spam trigger words, HTML quality, text-to-image ratio
- Engagement Score (20%) – Open rates, click rates, complaint rates
- Technical Score (10%) – Header validity, message formatting, unsubscribe handling
Red Flags That Tank Your Score
Watch out for these common deliverability killers:
- High bounce rates (>2%) indicate a dirty list
- Spam complaints above 0.1% trigger filters
- Sudden volume spikes look like spam campaigns
- Missing unsubscribe links violate CAN-SPAM
- URL shorteners (bit.ly) are associated with spam
- Suspicious attachments trigger security filters
Even one campaign with high complaints can damage your reputation for months.
Building and Maintaining a High Score
Improving your deliverability score is a marathon, not a sprint:
**List Hygiene** - Remove invalid addresses immediately - Re-engage or remove inactive subscribers - Use double opt-in for new subscribers
**Content Best Practices** - Consistent from name and address - Clear, relevant subject lines - Mobile-optimized design - Easy unsubscribe process
**Technical Excellence** - Warm up new IPs gradually - Maintain consistent sending patterns - Monitor feedback loops
**Engagement Focus** - Send to engaged segments first - Personalize content - Test and optimize send times