Changing root domains when adding a sending domain returns root_domain_mismatch

We’re moving our marketing email from crunchypupco.com to mycrunchypup.com within the same Klaviyo account.

Our existing branded sending domain is active, and we have a live welcome flow. Adding send.mycrunchypup.com returns root_domain_mismatch. The UI also requires the root domain to match the existing sending domain.

The migration documentation covers changing subdomains under the same root. What is the supported process for changing to a different root domain?

Specifically:

- Must we deactivate or remove the existing sending domain first?

- Should we pause the welcome flow, and how should we handle messages already queued?

- When should we update the sender addresses?

- What warming process applies to the new root domain?

We want to confirm the procedure before changing the active setup. The new domain already passes SPF, DKIM, and DMARC for Google Workspace email, but has not been configured for Klaviyo sending.