What is a list hygiene?
Also called: list cleaning, list decay
List hygiene is the ongoing removal of addresses that no longer work or no longer engage. Email lists decay at roughly 2% a month as people change jobs and abandon accounts, so a list left untouched for a year is materially worse than when you built it.
Decay is the part people underestimate. At 2% a month, a clean list of 50,000 contains around 11,000 dead addresses after a year without anyone doing anything wrong. That is a bounce rate well past the point where providers throttle.
Three habits cover most of it. Verify before any large send. Remove hard bounces immediately rather than at the end of a campaign. And suppress contacts who have not engaged in six to twelve months, because sending to people who never open is a negative signal even when the address is perfectly valid.
This recurring shape is also why per-address pricing gets expensive: the work is not one-off, so a cost model that bills every pass bills you for the same list several times a year.
Last reviewed 2026-09-11