Hrm.... mysite.com doesn't seem to be pointing to us.... perhaps you'd like to clue us in to the real name?
[ Note: The webmail problem has been identified and fixed - should be working now. ]
We don't generally do wildcard DNS records for shared hosting customers. For one thing, you need to have a unique IP for it to work properly, and for another, this lets people create subdomains without adding them directly in our system. There's also currently no way to add such a DNS record from the web panel.
If you have a specific application that requires this, let us know (via support) and I'll see what I can do.