List Hygiene
The ongoing practice of removing invalid, inactive, and risky addresses from your email list.
List hygiene is the routine of keeping only valid, reachable and interested people on your email list. It covers removing hard bounces and spam complainers, honoring unsubscribes, catching typos and fake addresses at signup, and retiring subscribers who have stopped engaging. Clean lists protect sender reputation and lower costs, since most email platforms price by contact count.
How to keep a list clean
Let your platform suppress hard bounces, spam complaints and unsubscribes automatically, and never re-import those addresses. In the US, CAN-SPAM requires opt-outs to be honored within 10 business days, and Yahoo asks bulk senders to process unsubscribes within 2 days.
Verify any imported or older list with an email verification tool before sending to it. Define "inactive" for your own sending pattern (for example, no clicks in six months), send those subscribers a short re-engagement series, then suppress those who do not respond.
What to remove, and when
After every send: hard bounces, spam complaints and unsubscribes, which your platform should handle automatically. At signup: typos in common domains, disposable addresses and role addresses such as info@ if your form accepts them; real-time verification or double opt-in catches many of these. On a schedule: subscribers with no clicks or purchases in the window you chose, after a re-engagement attempt. Before any import: the whole file, through a verification tool.
Common list hygiene mistakes
Judging inactivity by opens alone, which Apple Mail Privacy Protection inflates. Keeping unengaged contacts because a large list looks good: they cost money on contact-based pricing and drag down engagement. Deleting removed contacts outright when you need a suppression record to stop them being re-added later. Buying lists, which no amount of cleaning makes safe.
Sources
Related terms
Hard Bounce
A permanent delivery failure — the address does not exist or the domain is invalid.
Spam Trap
An email address used by inbox providers and blocklists to identify careless senders.
Sender Reputation
A score inbox providers assign to your sending domain and IP based on engagement, complaints, and bounces.