Hello @Giorgio Pezzuto , Thank you for reaching out. As the question is tagged for Azure Web App, to MAP an A record you need the web app's external IP address. You can find the IP address on the portal as shown here in the documentation.
- In the left pane of your app page, select Custom domains.
- Copy the ID in the Custom Domain Verification ID box in the Custom Domains page for the next step.
Hope this helps. Please let me know if this does not help resolve the issue, I will be glad continue with our discussion. Thank you!