I have a client who manages their own DNS - all the A records and CNAME records for example.com and a number of subdomains.
They want to use a dedicated subdomain for email - em.example.com. They want my company to manage the emails - not just the MTA but the MX records and SPF records. For this purpose, they want to delegate this subdomain to us, using an NS record.
My company is happy with this, in principle - we'd have the ability to update SPF records etc without having responsibility for the entire top-level domain - but we've hit a problem, our registrar / DNS provider doesn't support it. They won't allow us to add records for a zone that isn't registered with them.
How should I proceed? Do I have to find a new provider? What other options does anyone suggest?