I would tend to agree but would not suggest an asp.net app. .Net window application/console/service would probably be more intune with what your suggesting. asp.net apps. would not be able to hold a session long enough to do any real mass mailing...
The implementation of System.NET mail in Winform, Console and Asp.net uses different Config files required in app.config for Winform, Console and Web.Config in Asp.net. So what you can do with Asp.net depends on skill and the person without skills could buy existing component for a few dollars. In .NET 4.0 SSL can also be defined in the config file and not code and all of the above require .NET 2.0 and up.
Kind regards,
Gift Peddie