List hygiene is the ongoing removal of invalid, inactive, and risky addresses from a mailing list, plus verification of new addresses at the point of capture.
What good looks like#
- Done: Verify new signups in real time with an API and use double opt-in for marketing lists.
- Done: Suppress hard bounces immediately and soft bounces after 3 consecutive failures.
- Done: Run a re-engagement campaign at 90 days of inactivity and sunset at 180.
- Done: Remove role accounts (info@, sales@) and disposable domains from marketing lists.
- Done: Audit the list quarterly with a bulk verification service.
What bad looks like#
- Seen in audits: Importing old exports without verification.
- Seen in audits: Keeping unengaged contacts because the list size looks good in reports.
How to move from bad to good#
Work through the good list in order and re-verify after each change. Most teams find one or two items from the bad list already present; fixing those usually produces the largest improvement.
Frequently asked questions#
What is a spam trap?
An address that never opted in, maintained by providers and blocklists to catch senders with poor acquisition practices. Hitting one can blocklist your IP or domain.
What bounce rate is acceptable?
Under 2% hard bounces. Above 5% typically triggers ESP account reviews.