Copy the TXT record info in Apple Business Manager
If you receive a mail message asking you to verify ownership of your domain, another organization has claimed the domain you are using for some or all of your Managed Apple IDs. To verify that you own the domain, you must create a TXT record on your DNS server with the content provided in Apple Business Manager within 4 days of receiving this notification.
Copy the TXT record
In Apple Business Manager , sign in with an account that has the role of Administrator, Site Manager, or People Manager.
Click Settings at the bottom of the sidebar, then click Accounts below Organization Settings.
Copy the information below the label “TXT/MX Record”, then do one of the following:
Paste the information in a mail message to your DNS administrator
Create a DNS TXT record and paste in the copied information, then save and restart your DNS service.
Verify the new DNS record is working, then click Check Now.
The check will take up to 3 days to complete.
Important: If the check succeeds, Apple will contact you with more information. If the check fails, you must rename the Managed Apple IDs in that domain.