Measuring the impact of email deliverability on key business outcomes is essential for optimizing email marketing performance. By connecting deliverability metrics to broader metrics like customer lifetime value, retention, and revenue, marketers can identify opportunities to improve campaigns and drive tangible results. This comprehensive guide explores methods for correlating deliverability data with business KPIs, provides step-by-step implementation guides, and shares best practices.
Understanding Email Deliverability Metrics
Before diving into connecting deliverability to business outcomes, it's important to have a solid grasp of key deliverability metrics:
Delivery Rate
The percentage of emails accepted by the receiving mail server. A high delivery rate is necessary, but it doesn't tell you whether a message reached the inbox or the spam folder.
Inbox Placement Rate
The percentage of delivered emails that land in the inbox rather than the spam folder. It is usually estimated with seed-list tests and mailbox provider data such as Google Postmaster Tools, because senders can't see recipients' folders directly.
Bounce Rate
The percentage of emails that fail to deliver and "bounce" back. A high bounce rate can damage sender reputation and hinder future deliverability.
Spam Complaint Rate
The percentage of subscribers who mark your emails as spam. High complaint rates are a major red flag to inbox providers and can severely impact deliverability.
The following diagram illustrates the key components of email deliverability and how they impact overall performance:
Connecting Deliverability to Customer Lifetime Value (CLV)
Customer lifetime value represents the total worth of a customer to your business over the course of their relationship with you. Deliverability can have a significant impact on CLV:
- Higher deliverability means more opportunities to engage customers and drive purchases over time
- Consistent inbox placement builds trust and keeps your brand top-of-mind
- Deliverability issues lead to missed revenue opportunities and churn
To connect deliverability and CLV:
- Segment customers by deliverability (high vs. low inbox placement)
- Calculate average CLV for each segment
- Compare CLV between segments to quantify deliverability impact
- Implement deliverability improvements and track CLV changes
Deliverability Impact on Retention Rates
Strong email deliverability is also critical for retaining customers over time. When your emails consistently land in the inbox, you're able to keep customers engaged and coming back.
To measure deliverability impact on retention:
- Define cohorts based on join date and deliverability rates
- Track retention by cohort over 3, 6, and 12 month periods
- Compare retention between high and low deliverability cohorts
- Calculate the impact of deliverability improvements on retention
Retention Analysis Example
| Cohort | Deliverability | Month 3 | Month 6 | Month 12 |
|---|---|---|---|---|
| Cohort A | 95% | 75% | 60% | 50% |
| Cohort B | 80% | 65% | 45% | 35% |
In this illustrative example, the high deliverability cohort retained 10-15 percentage points more customers over a 12 month period. Check whether other differences between the cohorts, such as acquisition source, could explain part of the gap.
Attributing Revenue to Email Deliverability
Ultimately, the goal is to understand how email deliverability contributes to overall revenue. By attributing sales to email campaigns and factoring in deliverability, you can quantify the monetary impact.
Step 1: Implement Email Attribution Tracking
First, ensure you have proper attribution in place to tie email campaigns to downstream purchases and revenue. Common methods include:
- UTM parameters on email links
- Unique coupon codes per campaign
- Post-purchase surveys
Step 2: Calculate Revenue per Delivered Email
With attribution data flowing, you can calculate the average revenue generated per delivered email:
Revenue Per Delivered Email = Total Email Attributed Revenue / Number of Delivered EmailsTrack this metric over time to measure the effectiveness of optimizations.
Step 3: Quantify Missed Revenue Opportunities
To understand the impact of deliverability issues, estimate the potential revenue lost from emails that fail to reach the inbox:
Missed Revenue = Revenue Per Delivered Email * (Bounced Emails + Estimated Emails Placed in Spam)This is a rough estimate of revenue you could be capturing by improving deliverability. Use it to prioritize and get buy-in for optimization efforts.
The following diagram shows how email revenue attribution and deliverability metrics can be used to identify gaps and opportunities:
Deliverability Optimization Best Practices
Now that you understand the impact of deliverability on key business metrics, implement these proven best practices to improve your numbers:
Regularly clean your email list by removing inactive and invalid addresses. This improves deliverability and sender reputation.
- Remove hard bounces immediately
- Segment out unengaged subscribers (no clicks or other activity in 6+ months; opens alone are unreliable because of privacy features)
- Run email validation on older list segments
Properly authenticate your emails to improve deliverability and protect your brand from spoofing. Key authentication protocols include:
- SPF (Sender Policy Framework)
- DKIM (DomainKeys Identified Mail)
- DMARC (Domain-based Message Authentication, Reporting and Conformance)
Pro Tip: Use DMARC aggregate and forensic reports to monitor authentication and identify sources of spoofing.
Ensure your email content follows deliverability best practices:
- Avoid spam trigger words in subject lines
- Balance image-to-text ratio
- Use engaging, relevant content for your audience
- Include clear unsubscribe options
Example: Instead of "SALE! 50% Off Now!" try "Your exclusive offer - up to 50% off top brands".
Proactively monitor major blocklists and protect your list from spam traps to catch issues early:
- Check your sending IPs and domains against major blocklists such as Spamhaus
- Set up automated alerts for any blocklisting events
- Avoid spam traps with confirmed opt-in, address validation and removal of long-inactive subscribers; trap addresses are not disclosed, so you can't find and delete them directly
Warning: Hitting spam traps can quickly damage your sender reputation and lead to blocklisting. Find and fix the list source that caused it before you request delisting.
Conclusion and Next Steps
Email deliverability has a direct and measurable impact on critical business outcomes like customer value, retention, and overall revenue. By connecting deliverability metrics to these KPIs, you can build a strong business case for prioritizing deliverability optimization.
To start driving meaningful results:
- Benchmark your current deliverability metrics and KPIs
- Identify high-priority issues and optimization opportunities
- Implement quick wins like list cleaning and authentication
- Establish a deliverability monitoring and optimization process
- Measure results and adjust your approach over time
With focus and continuous improvement, better email deliverability will pay dividends across your key business metrics. Implement these strategies to maximize the ROI of your email marketing program.