Every email list decays. People change jobs, abandon email addresses, set up catch-all inboxes, and simply stop opening. Left unchecked, a decaying list will erode your sender reputation and bury your active recipients in a pile of bad data.
This Week’s Lesson
Email list decay happens at a rate of roughly 22% per year — meaning that without any active hygiene, more than one in five of your contacts will be unreachable within 12 months.
Hard bounces occur when an email is sent to an address that doesn't exist or has been permanently disabled. A bounce rate above 2% is a major spam signal. ESPs will start throttling or suspending your account. Hard bounces should be removed immediately after the first occurrence.
Soft bounces are temporary failures — the inbox is full, the server is temporarily down. These can become hard bounces over time. Most ESPs automatically suppress addresses after 3-5 consecutive soft bounces.
Inactive contacts are those who have never opened, clicked, or replied to any of your emails in a defined time window (typically 6-12 months). They're not hard bouncing — they're just ignoring you. Sending to them tanks your engagement rate and wastes your quota.
List hygiene actions to perform regularly: Remove hard bounces immediately. Suppress contacts after repeated soft bounces. Identify inactive segments (6+ months no engagement). Run re-engagement campaigns before deleting inactives. Verify email addresses using tools like NeverBounce or ZeroBounce before large campaigns.
The emotional barrier to deleting contacts is real. Marketing teams often resist removing unengaged contacts because 'they paid to acquire them.' But those contacts are now liabilities, not assets.