Bulk Emailer

We currently have approx 300k customer records in our database which is split into in various tables ? We need a system for being able to send html or text only emails to these customers ? We will need to have a simple interface to run a query on the existing data so we can filter down prior to sending. Html emails will be built externally and will be ready to go. After running a query (this could include data from various tables) we would need to "load in" the prebuilt email and have the facility to insert plain text and then send out. ? This will also be used internally so no design is necessary but it needs to be reliable. ? We want the facility to be able to upload a spreadsheet of data that can integrate into the existing database or be a separate dataset that we can send to. ? We currently have an asp page that sends via our webserver’s smtp. Our developers usually arrange the dataset and we send via webserver’s smtp? by running the page.