As of now, you can remotely administer at the domain level. It is my understanding that server wide administration will be released in a future update.

Thanks, but how do I do it at the domain level?

From the ArGo Mail Server .NET User Interface, click the "Domain and Users" tab. Select the domain group you want to add an administrator for. Select the user from the list of users that you want to add domain administration to.
Right click and select EDIT (or hit F2). Select the "Web Interface" tab. On the bottom of the tab there are check boxes for "Domain Group Administrator" and "Server Administrator". Place a check in the box next to "Domain Group Administrator" and click OK. The next time you log into your web mail. The account that you added the Domain Administrator to will have a link on the upper left of the page that will say "Administer Domain Group"