So I have a Macbook. On my mail application, I haven't been able to get it to work correctly. I have 4 email addresses: AOL, Yahoo, Hotmail, and my school email. My AOL account works perfectly. On the other hand, my school account (which is really my primary one now) doesn't let me send emails although I get them fine. And my hotmail and yahoo accounts don't work at all. Can anyone help me with this? It would be really appreciated.