http://ecom24.com/ has an application called "auto response plus" its bad ass for the price. I use it to deliver to a mailing list of around 350k
The speed of the deliver also depends on the server equipment you are using. A server just running the app on xeons will send aroudn 50k - 80k per hour. does open rate tracking, and you can build lists of people that opened certain mails..not bad for the price of i think $150. Its a good product at a reasonable price.