How to Clean a Mailchimp List Before You Send
· 4 min read
Mailchimp removes addresses that hard bounce, but only after you have already sent to them and taken the hit to your reputation. Verifying your audience before a send catches those addresses in advance, along with disposable inboxes and other contacts that are not worth paying for. This guide walks through cleaning a Mailchimp audience with NoBounch.
Mailchimp changes its menus from time to time, so the steps below describe where things are in general terms. If a button has moved, Mailchimp's own help pages on exporting, importing and archiving contacts have the current details.
Before you start
- Make sure you have permission to email the people in your audience. NoBounch is for your own opt-in lists, as set out in the acceptable use policy.
- Decide whether to clean the whole audience or one segment, for example contacts added a long time ago or people you have not mailed recently.
- Keep a copy of the original export, so you can always go back.
Step 1: Export your audience
In Mailchimp, open your audience and go to the list of all contacts. Use the export option to download the audience. Mailchimp prepares a file (a ZIP containing CSV files) that includes subscribed contacts and, separately, unsubscribed and cleaned ones. You only need to verify the subscribed contacts, because Mailchimp already stops sending to the others.
If you only want to clean part of the audience, create a segment first and export that segment instead.
Step 2: Verify the file with NoBounch
- Sign in to NoBounch and open the bulk verification page.
- Upload the subscribed contacts CSV. NoBounch finds the email column automatically and keeps your other columns.
- Check the number of unique emails and credits, and start the check. Duplicates are removed before checking, so you never pay twice for the same address.
- When the list is finished, you get an email. Download the results.
You can download each result as its own file: valid, invalid, catch-all, disposable and unknown, or a full report with every row and the result columns added. More on how this works is on the bulk email verification page.
Step 3: Decide what to do with each result
| Result | Suggested action in Mailchimp |
|---|---|
| Valid | Keep. No change needed. |
| Invalid | Archive or unsubscribe. These would bounce. |
| Disposable | Archive or unsubscribe. Nobody reads these inboxes for long. |
| Catch-all | Keep, but tag them so you can send to them separately or watch their engagement. |
| Unknown | Keep for now and check again later. The credit for an unknown result is refunded. |
Step 4: Tag the contacts in Mailchimp
Tags make the next step easy and keep a record of what you did.
- Take the invalid and disposable files from NoBounch.
- Use Mailchimp's import option to import them into the same audience, choosing to update existing contacts and adding a tag such as
nobounch-remove. Make sure the import does not change anyone's subscription status unintentionally. - Do the same for the catch-all file with a tag such as
nobounch-catch-all.
Alternatively, import the full report and map the nb_result column to a Mailchimp field, so every contact carries its result.
Step 5: Archive or unsubscribe the bad contacts
Filter your contacts by the nobounch-remove tag, select them, and archive them. Archiving removes contacts from your audience without deleting their history, and archived contacts do not count toward your plan's contact limit. You can unarchive them later if needed. Unsubscribing is the alternative if you prefer to keep them visible in the audience.
Avoid permanently deleting contacts unless you are sure. Permanent deletion removes their history and, in Mailchimp, prevents you from re-importing those addresses.
Step 6: Send smarter
- Exclude the catch-all tag from your main send, and mail those contacts in a smaller batch. Read what is a catch-all email for why.
- Keep an eye on bounces after the send. The email bounce codes reference explains what each one means.
Common questions
Will cleaning remove real subscribers? Invalid results are mailboxes that do not exist, so removing them does not lose anyone who could read your mail. Catch-all and unknown results are kept, which is why they are worth tagging rather than deleting.
Should I clean cleaned contacts too? No. Mailchimp already stops sending to contacts it has marked as cleaned after a hard bounce, so verifying them again adds nothing.
How long does it take? Small lists finish in minutes. Larger lists run in the background, and NoBounch emails you when the results are ready.
Keep the audience clean
Cleaning once helps, but lists keep decaying. Re-verify before mailing segments you have not used for a few months, and check new signups as they arrive with the email verification API. Read email list decay for a sensible schedule. Using HubSpot as well? See how to clean a HubSpot contact list.