I'm looking for a person who can send email campaign to 500k recipients using MailChimp.
You must use MailChimp because it has the best delivery rate there is, and it's free test package is the largest (2000 emails)
The difficulty is that MailChimp requires to verify your list before sending it if it's over 2000.
The easiest way to bypass this limitation is to use different account opened from different IPs (in this case 250 of them).
Other options is to verify the account and and buy package to send 500k. But there is a risk that MailChimp may freeze your account if there are some spam complaints or high bounce rate.