Best approach to send 0.5 million emails with lowest cost [closed]


I am from engineering background. I have to send 0.5 million emails to users. I already have email addresses of the users.

I have few confusions

  • Sending mail through sendgrid etc, do I need to buy subscription which can hold 0.5 contacts?

  • I want to send via API, is there any API only approach?

  • What if I send via gmail SMTP?

Any kind of information is highly appreciated.