TL;DR
- Mailchimp marks an address cleaned only after it bounces, so every dead address costs you one bounce first.
- Subscribed, unsubscribed and non-subscribed contacts all count toward your contact limit. Archived contacts don't count toward your billing tier.
- Verify the audience in MailExchange (from $0.0058 per email), then archive undeliverable contacts before your next send.
Why Mailchimp's own cleaning isn't enough
Mailchimp's help center says "hard bounces and repeated soft bounces become cleaned contacts." That keeps a bad address from bouncing twice, but the first bounce has already happened, on your domain and in your campaign report. Import an old list of 20,000 and the cleaning happens one bounce at a time during your next campaign.
Verifying before you send finds most of those addresses without sending anything. MailExchange checks syntax, DNS and MX records, risk lists, and the mailbox itself over SMTP, and stops before any email is delivered. How verification works.
Fewer billable contacts
According to Mailchimp, subscribed, unsubscribed and non-subscribed contacts all count toward the monthly contact limit, and cleaned contacts don't. Mailchimp also says "archived contacts don't count toward your billing tier," and archived contacts keep their data and can be unarchived later.
So a dead address sitting in your audience as subscribed costs you twice: it counts toward your plan, and it will bounce on the next send. Find those addresses, archive them, and both problems go away.
Sources: About your contacts and Archive and unarchive contacts, Mailchimp help center, checked 2026-10-17.
How to clean a Mailchimp audience
- Export your audience from Mailchimp as a CSV. Subscribed contacts matter most, since they're the ones you'll email.
- Upload it to MailExchange. Duplicates are free and unknowns are refunded.
- Download the undeliverable rows (and any risky rows you decide to drop).
- Import that file back into Mailchimp with a tag, for example mx-undeliverable, updating existing contacts.
- Filter the audience by that tag and archive the contacts. They stop counting toward your billing tier, and nobody sends to them by accident.
What to do with each result
| MailExchange result | What to do in Mailchimp |
|---|---|
| deliverable | Keep. |
| risky: catch-all | Keep if they opted in. These domains accept any address, so watch their bounces. More on catch-alls. |
| risky: role | Keep if they're customers. Role inboxes (info@, office@) are real but shared. |
| risky: disposable | Archive. Throwaway inboxes rarely read anything. |
| undeliverable | Archive (or delete). They will bounce. |
| unknown | Keep and re-check later. The credit is refunded. |
How often to clean
Clean before any send to a segment you haven't emailed in a few months, after importing any list from outside Mailchimp, and once or twice a year for the whole audience. Addresses decay as people change jobs and providers close inboxes, and older lists bounce more.
What it costs
Pay as you go: 5,000 emails for $29, 25,000 for $99, 100,000 for $299. Credits never expire, so you can clean once a quarter without losing a monthly allowance. Monthly plans are 15% off. See pricing or estimate your list with the verification cost calculator.
Stop bad addresses at signup
Most bad addresses in a newsletter list come from signup forms: typos, fake addresses and disposable inboxes. The form widget and the API (both in early access) check an address before it reaches Mailchimp. You can also verify new subscribers automatically with a Zapier webhook step. A native Mailchimp connector is on our roadmap.