Some terms seem to be mixed up here.
Rather than saying "email CNAME" (which is a misnomer) let's say go.coffee-cups.com is the branding domain (that's Marketo's term for the email click tracking server).
Because all your links will be rewritten to go.coffee-cups.com/<unique id> it doesn't matter that the final destination after that would be www.coffee-mugs.net or pages.coffee-mugs.net.
The principal restriction is that the branding domain, landing page domain(s), and Reply-To/From domains* must be different.
* Note I'm using "domain" here as Marketo does -- meaning, more technically, "hostname-as-domain."
In Marketo-speak, pages.example.com and www.example.com, despite sharing the parent domain suffix
example.com, are not the same "domain". In a discussion among technical people the meanings are different.
I guess my main question was meant to reference the pieces that their IT will need to implement.
Branding name: go.coffee-cups.com
Domain Alias: go2.smartcoffee.com redirecting to the unsubscribe page
For their IT, they will need to create a DNS Record for the new LP CNAME and Email CNAME and point them to the appropriate place. Will this matter if it's a different domain, or can they simply create two separate entries?
Again, just to reduce confusion when communicating on DNS matters with IT:
- When you set up a DNS CNAME record pointing go.coffee-cups.com to mkto-<nnnn>.com, go.coffee-cups.com is not called "the CNAME". Rather, mkto-<nnnn>.com is the CNAME and go.coffee-cups.com is called the DNS Alias. (The Alias is the left-hand-side of the DNS CNAME record.)
- Likewise, when you have a CNAME record pointing go2.smartcoffee.com to <account string>.mktoweb.com, "the CNAME" is <account string>.mktoweb.com; the Alias is go2.smartcoffee.com.
In other words, what inexperienced people call "the CNAME" is actually the opposite, which can cause immense confusion when dealing with DNS experts.
Also, if go2.smartcoffee.com is the client's only LP domain, it's not called a "Domain Alias" in Marketo; in Marketo, that's just the Landing Page Domain Name. Domain Aliases are added only if you want a Marketo instance to serve LPs from more than one hostname. They aren't required for an instance to run.
As far as using different domains (meaning different private domain suffixes, like example.org and example2.info) for different purposes, that's fine. Doesn't matter what DNS zones the CNAME records exist in. They can be in the same zone or different zones, long as they're pointing to the right Marketo property.