What email list hygiene is#
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.
Why it matters#
Bounces, spam traps, and disengaged recipients are the three fastest ways to damage reputation, and all three are prevented by hygiene.
How mailbox providers use it#
Gmail, Microsoft, and Yahoo combine authentication results, sender reputation, and recipient engagement into a placement decision made per message. Email list hygiene feeds directly into that model, and weaknesses compound with other signals.
How to measure the impact#
- Baseline inbox placement with seed tests before any change.
- Make one change at a time and hold volume steady.
- Re-test after 48 to 72 hours; provider models need time to update.
- Track Postmaster Tools and SNDS alongside your seed results.
Improving it#
- Verify new signups in real time with an API and use double opt-in for marketing lists.
- Suppress hard bounces immediately and soft bounces after 3 consecutive failures.
- Run a re-engagement campaign at 90 days of inactivity and sunset at 180.
- Remove role accounts (info@, sales@) and disposable domains from marketing lists.
- Audit the list quarterly with a bulk verification service.
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.