Mailchimp to Klaviyo: Get the Suppressions Right, Then Verify

SimpleVerifier Team·3 November 2026·2 min read

Key takeaways

Klaviyo's Mailchimp integration syncs subscriber info including unsubscribes and cleaned contacts, audiences as lists, received/opened/clicked events from the last 90 days, and Mailchimp ratings. Tags and custom audience fields don't sync.
An existing Klaviyo profile is suppressed by the sync only when the incoming Mailchimp status has a newer timestamp. If someone who should be suppressed isn't, export them from Mailchimp and upload them to Klaviyo's suppression list.
Cleaning contacts in Mailchimp while the integration is still connected suppresses them in Klaviyo. Remove the integration first if you don't want that.
If Mailchimp is connected to your Shopify store, disconnect it before integrating Mailchimp with Klaviyo, or double opt-in emails may go to existing subscribers.
After the sync, verify the subscribed profiles before the first Klaviyo campaign; the integration moves statuses, it doesn't check mailboxes.

The integration moves statuses; it doesn't check mailboxes. Klaviyo's Mailchimp integration brings subscribers, unsubscribes and cleaned contacts across, but suppression depends on timestamps and the order you do things in. Get the order right, then verify what Klaviyo will actually email, and the first Klaviyo campaign won't undo your Mailchimp hygiene.

Sources, read 2 November 2026: Klaviyo Help Center how to migrate from Mailchimp, how to migrate existing subscribers and unsubscribes into Klaviyo and how to migrate from another ESP.

What the integration does

Item	Klaviyo's Mailchimp integration
Subscriber info	Synced, including unsubscribes and cleaned contacts
Audiences	Become Klaviyo lists
Engagement	Received, opened, clicked for campaigns sent in the last 90 days (not A/B tests)
Tags, custom audience fields	Not synced; export and import as custom properties
Existing Klaviyo profiles	Suppressed only if the Mailchimp status has a newer timestamp
Deleted in Mailchimp	Not deleted in Klaviyo
Cleaning in Mailchimp while connected	Those contacts get suppressed in Klaviyo
Shopify connected to both	Risk of double opt-in emails to existing subscribers

The order that works

Disconnect Mailchimp from Shopify if both are linked, before anything else.
Connect the integration with a Mailchimp API key, and choose engagement data and audiences under Advanced.
Check suppressions. In Klaviyo, open the suppressed profiles view and compare counts with Mailchimp's unsubscribed and cleaned totals. For anyone missing, export from Mailchimp and upload a single-column CSV to the suppression list. The Mailchimp export steps show where those statuses live, and compare email lists shows who's missing.
Bring tags across as a CSV of custom properties.
Remove the integration once Mailchimp is retired, and only then clean anything in Mailchimp you don't want suppressed in Klaviyo.
Verify the emailable profiles. Export the subscribed list from Klaviyo, verify it on the verify page, and suppress invalid results. The Klaviyo list cleaner formats the export.
First sends to recent engagers. The 90 days of synced engagement lets you build that segment from day one.

What verification can't settle

Some addresses won't confirm either way: catch-all domains accept everything, and Microsoft consumer mailboxes (outlook.com, hotmail.com) often don't answer single-mailbox checks reliably. Leave those for later sends. Verification also can't tell you who still wants your mail; Klaviyo bills on profiles it can email, so a sunset step matters as much as the bounce clean-up. Clean a Klaviyo list covers what to do once you've settled in.

Where SimpleVerifier fits

Verify the migrated list on the verify page; the first 100 checks are free with a Google sign-in. Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off. If deliverability drops after the move anyway, see deliverability dropped after an ESP migration. Plans are on pricing.

Common questions

Does Klaviyo's Mailchimp integration bring over unsubscribes and bounces?

It syncs subscriber info including unsubscribes and cleaned contacts. Suppression of profiles that already existed in Klaviyo depends on timestamps, so check the suppressed profiles list afterwards and upload any that were missed.

Do Mailchimp tags transfer to Klaviyo?

No. Klaviyo's guide says tags and custom audience fields don't sync; export them as a CSV and import them as custom profile properties.

Why did my subscribers get double opt-in emails after connecting Mailchimp to Klaviyo?

Klaviyo warns this can happen when Mailchimp is still connected to a Shopify store that's also connected to Klaviyo. Disconnect Mailchimp from Shopify before integrating Mailchimp with Klaviyo.

Should I verify the list before or after the Klaviyo sync?

After the sync, on the subscribed profiles Klaviyo can email. The sync handles statuses; a verification pass then finds addresses that stopped working since Mailchimp last sent to them, which matters most if you sent rarely.

Check your list before you send

Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.