Send 50 000 emails in txt with assurance they arrive to their recipient for 96%

Hi, I have a prospects file for a project. It is in .CSV in two field separated by ";" (email;first name). I need to send them and to be sure most of part the 50 000 emails will arrive to their recipient. The email will be written in txt and will have an opt-out option. I need a really sure smtp server. Offer me your best solution.