I need help with making the lowest cost highest deliverability bulk email smtp

I need help setting up the lowest cost smtp that delivers thousands of emails daily with no problem using gmass integration with this smtp or other option that will get the job done easily. I want the least complicated options that don't require me to keep going back and forth with the vps talking about who I'm emailing. I would like the process written down for me to understand towards the end. Please do your best to make this the lowest cost option possible.