Sending rules and list practice
What is email data decay?
Also called: list decay, contact data decay
Data decay is the steady loss of accuracy in a contact list as time passes. People change jobs, companies rebrand or close, mailboxes are deleted and phone numbers are reassigned, so a list that was clean when built gets worse every month without anyone doing anything wrong.
B2B lists decay faster than consumer lists because work addresses are tied to a job. When someone leaves, their mailbox is usually closed, and the next email to it hard bounces.
Decay is the reason verification is a recurring task rather than a one-off. A result from last quarter tells you the address worked last quarter.
The practical rule is to verify before each large send, and always before mailing a list that has sat unused. Any vendor figure for a monthly decay rate is an estimate that varies by industry and source, so measure your own: verify the same list twice a few months apart and compare.
How SimpleVerifier handles it
A confirmed result is reused for at most 14 days. After that the next check probes the mail server again, because a mailbox that existed then may be closed now.
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By SimpleVerifier Team · Last reviewed 2026-10-13 · All 50 glossary terms