How to clean an email list

What to remove

• Hard bounces: addresses that failed permanently. Every send to them tells mailbox providers you do not look after your list.
• Invalid addresses: broken syntax, domains that do not exist or take no mail, mailboxes the receiving server rejects.
• Disposable addresses: temporary inboxes that stop working soon after signup.
• Duplicates: the same person twice gets your mail twice and complains once.
• Complaints and unsubscribes: keep them suppressed, never re-import them.
• Long-inactive subscribers: after a re-engagement attempt, not before.

Role addresses (info@, sales@) and addresses on accept-all domains are judgement calls: often real, never certain. How to handle catch-all addresses

1. Export the list with its history

Export contacts as CSV from your email platform or CRM, with the columns that say how each contact behaves: signup date, last click, last purchase. Leave out anyone the platform already suppresses.

2. Remove what you already know is bad

Hard bounces, spam complaints and unsubscribes from your platform's own reports go first. They need no checking, and unsubscribed addresses must stay out by law in most countries.

3. Verify the rest

Run the remaining addresses through a bulk email verifier: syntax, domain, MX and a mailbox check that sends nothing. Remove undeliverable addresses, drop disposable ones, and keep unknown results for a second check later.

4. Decide on risky addresses

Keep accept-all and role addresses that clicked or replied recently. Put the others in their own segment and mail it at lower volume first, watching bounces.

5. Re-engage before you remove

Send inactive subscribers one or two messages asking whether they still want your mail, and remove those who do not respond. Judge activity by clicks and replies rather than opens: privacy features in mail apps, such as Apple Mail Privacy Protection, load images automatically and make opens unreliable.

6. Import back and keep it clean

Import the clean file, keep the removed addresses on the platform's suppression list so they do not come back with the next import, and verify new addresses as they arrive, at the signup form, so the list stays clean.

How often to clean

Before any send to a list you have not mailed for a few months, and on a regular schedule for lists you mail often; many senders clean quarterly. Verifying at signup keeps most bad addresses from ever getting in. Bounce and complaint rates are what mailbox providers watch: what Gmail, Yahoo and Microsoft require from bulk senders.