What Is Email List Decay?
Email list decay refers to the natural degradation of email list quality over time. Even a perfectly clean, organically-built list will contain invalid addresses within months because people's circumstances change constantly.
The Numbers: How Fast Do Lists Decay?
Research consistently shows email lists decay at 22-30% annually. Here's what that means in practice:
- A list of 10,000 emails loses 2,200-3,000 addresses per year
- After 2 years, 40-50% of your original list may be invalid
- B2B lists decay faster than B2C (higher job turnover)
Why Do Email Addresses Go Bad?
1. Job Changes
The average person changes jobs every 4 years. When they leave, their corporate email often gets:
- Deactivated immediately
- Forwarded temporarily then deleted
- Converted to an auto-reply for 30-90 days
B2B email lists are particularly vulnerable. In tech industries with higher turnover, decay rates can exceed 30% annually.
2. Email Provider Changes
People switch email providers for many reasons:
- Moving from ISP email (comcast.net) to Gmail
- Graduating and losing .edu addresses
- Consolidating multiple accounts
- Privacy concerns driving switches to ProtonMail, etc.
3. Domain Abandonment
Small businesses fail, companies merge, and domains expire. When a domain goes away, every email address at that domain becomes permanently invalid.
4. Mailbox Abandonment
Some addresses technically exist but are never checked:
- Secondary accounts created for signups
- Addresses abandoned after spam overwhelmed them
- Accounts from services people stopped using
Signs Your List Is Suffering From Decay
Watch for these warning signs:
- Rising bounce rates: Gradual increase over several campaigns
- Declining open rates: Fewer people engaging (or existing)
- More spam complaints: Long-dormant subscribers forgetting they signed up
- Blacklist appearances: Sending to too many bad addresses
Fighting List Decay
Prevention
- Use double opt-in to verify addresses at signup
- Implement real-time email validation on forms
- Send regular emails (dormant lists decay faster)
Maintenance
- Validate your entire list quarterly
- Remove hard bounces immediately
- Flag and monitor chronically inactive subscribers
- Run re-engagement campaigns before purging
Protect Your List's Value
Your email list is a depreciating asset that requires active maintenance. Regular validation with ValidateList helps you understand your list's true size and value while preventing the delivery issues that come from sending to decayed addresses.