Push to Database from WP or good Mail Software

Hello all,
new to the forums, but not new to WP. So I’m going to have an email newsletter sign-up form on all of my pages in a sidebar, and I need to construct a concise system for managing subscribers. The guy managing our servers wants to know if there is a way to push to a database or communicate with Exchange server so that the mailing list dynamically updates. Can this be achieved? Or do I need to implement 3rd party email newsletter software, and if so, what is recommended? I am really trying to avoid that because of cost, and my IT guy on the server end doesn’t like letting things outside our control. We are looking at ideally tens of thousands of people eventually for the newsletter as we are running a political campaign. Thanks so much!