I get it!
You can just use a redirect service. For me it's working pretty good.
Do this.
Follow all the steps in this tutorial
http://www.zymic.com/forum/index.php?showtopic=12474If you don't want to use a external provider os email (like google apps, you can just jump the step 5).
Now, create another "web host account" in Zymic. In the control panel of this account, create a domain name. What you wll do is to create your subdomain as a domain (so, you wll have two accounts, one with your domain and one with your subdomain).
Go back to and repeat the steps 6 to 8 of the tutorial.
Be happy!

I hope it's help.
Bye.