Email Setup on IPhone 6

I have set up a second email account on my IPhone. I have moved the second account up to the top of the lists of my two accounts. I can select All Inboxes to show the first and second account emails together. When I compose a new email, I would like to have the second email address as the From: in my emails. But for some reason it is showing the first account I set up. I know I can change it in each email I compose, but that is a huge waste of time. How do I permanently set the second account as the From: account on all emails composed while I am in the All Inboxes folder?