After the latest software upgrade to my iPhone, I have been unable to sign in to my mail icon what is the problem?

After latest software update to my iPhone 6, my mail washing pushing through. I researched and followed some of the tips one of which included deleting the mail app and reinstalling. Now I cannot get pass the welcome to mail and the different platforms. I hit iCloud and when I put my Apple ID it says that email is already in the system and fails to sign me in. How can I correct this?