Email blast to around 50,000 contacts - 2 seperate emails

I would like to send 2 emails to 50,000 subscribed contacts, idealy through sendy and AWS so they can be done fast.

I have had issues with paying people using there own SMTP relays and i will review the results after every 2000 sends before i pay. I have a dashboard and i can track views and opens and i will not agree to pay if i dont see atleast a 5% email open rate. All emails are cleaned, subscribed and i should be seeing a good rate of opens.