Delink DNS zone files

What’s the process for delinking DNS zone files and reverting back to a partner host?

You’d have to delete the zone from your account from the Overview tab.

What if I want to keep the site on Cloudflare, but just want to remove the mail DNS and have that remain on the host server?

You can delegate away a subdomain, such as ‘mail’, but you should discuss this with the host of that resource.

Personally, I keep all DNS records here and point them properly with “A” and “CNAME” records to standard resources that are compatible with third party DNS.