Adding CNAME for the root domain issue

[John Levine]

Assuming you mean this (notice the dots):

 Domain.com.  CNAME  x.y.com.
 www     CNAME x.y.com.

it should work.  Some people believe that you can't have other records
at names below a name with a CNAME, but they are mistaken.

On the other hand, this will not work.

  domain.com. CNAME x.y.com.
  domain.com. MX 10 server.somewhere

To make this work, you need Stephane's hack of copying the A and AAAA records.

R's,
John