Yes.
This is because PENs are independent of one another and have different web addresses. For example, the email2 Private Email Address can be accessed at: https://secure.email2.com/beta/web/ A different PEN would have a different web address (https://secure.email2.com/example2/web/ for instance).
Once you log in to the email2 Web Client, you only have access to that specific PEN.

