Dedicated server / SMTP server

I am looking for a professional with proven skills and have been worked in this area before with success. I want to buy a dedicated server with linux OS to install an email sender like (interspire, oempro, phplist.. whatever..) I look for someone that advice me the best server solution and configure it in order to sent emails reach inbox folder of my clients... it could be 500.000 emails in 12 hours. I ask you to consider balanced delivery or other solutions you advice. Once again, i ask you to answer only if you have previous experience on this matter.