Hello rotondim,
To successfully create a SmartDL you must have the following permissions at the container level (these are minimum permissions required):
Create Group Objects (allow) [This object only]
List Contents (allow) [This object and all child objects]
Read All Properties (allow) [This object and all child objects]
Write All Properties (allow) [This object and all child objects]
Read Permissions (allow) [This object and all child objects]
All Validated Writes (allow) [This object and all child objects]
All these permissions can be set using Active Directory Users & Computers with View->Advanced selected from the main window.
Additionally, if you want the email domain to be pre-populated when creating a group you must have a minimum of View Exchange Admin rights at the Exchange Organization level (this can be set via the Exchange System Manager).
It is important to note that even if your account has been granted the above permissions, you could experience problems if someone has denied permission to your account or a security group you are a member of. Deny permissions all override grant permissions.