Now you CNAME now you can’t

Yesterday at work I had a discussion with one of the guys in charge of our DNS. I asked him to create a CNAME record on one of the domains under our authority, pointing to an external canonical name, but he kindly refused. So I asked whether this was company policy of some kind, as I saw no technical reasons for this not to work, but he answered:

No, the problem is technical; the hostname one points to, has to be managed on the same DNS-platform and this can’t be done in this case as we’re not the SOA for the external domain

So to prove my point (yeah, that’s how I roll) I created a temporary CNAME-record on my own domain, pointing to the external hostname (much the same way is just an alias for but that did not convince my colleague either:

Making a SOA on a server where that isn’t allowed, is not really according to the standards.

As the change was pretty urgent and there weren’t any important downsides, I adapted my change request for the DNS-entry to be created as an A-record. But in the mean time I started reading up on CNAME’s on Wikipedia and glanced over the two relevant RFC’s (RFC 1034 and RFC 2181), but I really can’t find any confirmation of what my (respected) colleague is referring to. But I’m sure there are smarter people reading this here blogpost who might be able to explain what I am obviously missing, no?