This overload requires the license key be already set (such as with MailBee.Global.LicenseKey property, app.config, web.config, or in Windows registry).

This class on its own does not have any useful features. It mainly supports the licensing infrastructure. For instance, it lets you check how many days you still have in trial mode.

Note
You can avoid using Powerup class and unlock Smime and Impersonationclasses in Security namespace directly, by supplying the license key right in their constructor. See Smime(String) and Impersonation(String) constructors.

Reference