Yes, it is but you have to create an actual account in WHM.
Example:
Domain: subdomain.domain.com
You can limit the space that way. I'm sure there are other ways but this way seems the simplest. In addition, it has all the features of a regular account. E-mail, FTP, Cpanel, IP Address etc. Here's some information on FTP and E-mail so you don't get confused
FTP Address: ftp.subdomain.domain.com
Mail Servers:
mail.subdomain.domain.com
smtp.subdomain.domain.com
E-mail Address would be..
[email protected]
Hope this helps
Credanco
Creemsoda.com