Do I need a Mail Server to run ListManager?

No, you do not.

ListManager has its own mail server built-in and does not need to use another mail server. In fact, the mail engine included with ListManager is much faster than most any other mail package available, so by using a different mail engine to deliver mail you will actually be slowing down the performance of ListManager.

ListManager can receive and send Internet email on its own. If you want to run ListManager on a machine that already has a mail server installed, please see "Mail Server Coexistence".