No. Only a single user account can ever access Mailbox Administration or System Configuration at a time. It does not matter if this account is local or on a domain. Only a SINGLE user can ever be logged into the system at any one time. Also note ALL DuVoice applications must run with Administrator privileges on the local machine.
Yes, but not recommended. Typically joining a Windows domain causes a great deal of issues because domain restrictions are applied to services and applications making access to files and services impossible for the system. All DuVoice applications must run with Administrator privileges on the local machine.