Definition
An email list hygiene score combines multiple list quality indicators into a single metric for easy monitoring. Components typically include bounce rate as a percentage of total sends, spam complaint rate, engagement rate across the list, suppression rate (percentage of list in suppression status), list freshness measured by recency of data updates, and hard bounce accumulation rate. A declining hygiene score predicts future deliverability problems before inbox placement is affected.
Typical Score Components
- Bounce rate — lower is better; above 2% signals hygiene issues
- Spam complaint rate — below 0.1% is healthy; above 0.1% requires immediate attention
- Active engagement rate — percentage of list engaged in last 90 days
- Suppression rate — percentage of list currently suppressed for inactivity
- List freshness — recency of last cleaning and deduplication
Best Practices
- Calculate hygiene score monthly and track the trend direction
- Set a minimum hygiene score threshold that triggers automated list cleaning when breached
- Weight engagement rate most heavily since it is the strongest predictor of inbox placement
- Report hygiene score alongside other programme health metrics in monthly reviews
- Investigate hygiene components individually when the composite score declines to identify the root cause
Related Glossary Terms
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
ARPU (Average Revenue Per User)
ARPU (Average Revenue Per User) is a metric that measures the average revenue generated per email subscriber over a specific period, used to evaluate list value and campaign effectiveness.
Attention Rate
Attention rate is the percentage of email opens that last longer than 5 seconds, distinguishing genuine reads from passive opens, preview-pane views, or Apple MPP auto-loads.
Bounce Classification
Bounce classification uses SMTP codes (550, 551, 552, 553, 554, 450, 451, 452) and enhanced status codes to categorise permanent and transient delivery failures.
Bounce Rate Threshold
A bounce rate threshold is the percentage of hard or soft bounces at which email platforms and ISPs begin to penalise sender reputation, typically around 2-5%.
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.