experCheckBut = Checkbutton(text = "Activate the experimental features?", command = exper.active, variable = experBool).grid()
SMPTEntry = Entry(state = DISABLED, textvariable = SMTPVar).grid()

## I'm essentially looking for the .config() syntax. ##

class exper:

    def active():
        print(experBool.get())

        #On click activate and deactivate experimental features.

        if experBool.get():
            SMTPEntry.config(state = ENABLED)
            experBool.set(True)

        else:
            SMTPEntry.config(state = DISBALED)
            experBool.set(False)