You want to generate a new meeting ID as the default (authenticated meetings) and you run the LYNC Server Management cmdlet Set-CsMeetingConfiguration –DesignateAsPresenter None. However, it appears you still have to choose the “customize” checkbox before it will default to a private meeting. Without choosing customize it will still create a public meeting (using the static meet ID). If you click the customize box in the outlook add-in and click remember settings, add-in will create private meeting every time you schedule a meeting. If you don’t customize the options in the add-in or remove the checkbox it will create a public meeting with static meeting ID.
Using the LYNC Server Management Shell there are two switches for the cmdlet Set-CsMeetingConfiguration that can affect this.
If you set EnableAssignedConferenceType to false, there is now, no checkbox to customize settings
When EnableAssignedConferenceType is set to false, outlook will always create a new private meeting with different meeting id.