Switch MS O365 name servers to another dns hosting service?

Currently we have client which is using Office365 for DNS hosting and also for email delivery.

The domain is registered at an external registrar, but unfortunally the MS name servers have been used in the past for DNS management.

The domain is like abcdef.com and all accounts and emails are setup as @abcdef.com. Now the client needs use subdomain emails, like [email protected].

Unfortunally MS does NOT support this setup, when using the microsoft nameservers, for this we have to use external name servers...

We have now duplicated all DNS records to the new DNS provider and changed all name server entries at the registrar, and everything still works :)

But now we need to tell office 365 to also use the external name servers and not the MS name servers, but so far we have not found a way to do this.

We can't delete the domain in office 365, otherwise we loose all @abcdef.com access/logins/email addresses.

Any ideas on how to proceed on this?

This is just to simple to find, shame on me

From here: https://answers.microsoft.com/en-us/msoffice/forum/all/office-365-admin-domains-says-my-domain-is-managed/007993a9-b8d6-4593-9ba2-b6e886612626

1. Navigate to your Office 365 Admin Center > Setup > Domains.

2. Select your custom domain > DNS management.

3. Choose I'll manage my own DNS records under the Set up your online services section.

4. Change the name servers to point to your registrar.

5. Add the DNS records required for Office 365 to work.