Let's say I've registered domain.com at enom and set it up to use Google Apps for email by rerouting DNS to enom's servers and editing the MX records there. That works flawlessly. Now let's say I want to have email at a subdomain for that same site. I already have a working subdomain at the host, but I want to catch email traffic at enom before it gets that far. I've set up Google Apps as a new account for the subdomain, successfully verified domain ownership, and now they want me to update MX records. What's the right format?

For domain.com, I just put @ for the hostname, and then provided the Address and Pref values that Google gave me. I tried putting subdomain.domain.com as new values under hostname for the subdomain, but that doesn't seem to work. What am I doing wrong?