Sending Thousands of Newsletters a day through wordpress plugin

Hello,

I have a list of emails of people who have subscribed to get newsletters from my site. Constant contact and mailchimp are way out of my budget, So i was looking for a simple solution to blast out these emails from my server.

We tried mailpress, but its just not working. Does anyone have any suggestions to another plugin I could try, that possibly offers support to help set it up?