Whats Going On?!

Recently had my gmail and yahoo emails on the email app thats automatically included with iPhones. Kept telling me that yahoo email password needed to be re-entered but then wouldnt let me (its the correct password) so got this app. Still wont let me! Saying its been denied by server. I just need to have my email accessible on my phone and I hate the Yahoo Mail app ?

joellygalaviz about Email - Edison Mail, v1.4.3