Apple Mail not working with Office 365 Exchange account. Not accepting password.

I have an email coming in from a website hosted on Godaddy that quit accepting the password and delivering mail. I discovered from Godaddy that office 365 has changed their format and wanted to be set up using an exchange account. I did this and now I have a new emails to this account and tons left on the old one that won't babe transferred. Thankfully I can NOW get emails BUT I cannot send any, it still says the password isn't right... I have changed the password, and Godaddy suggested I just start using Outlook as my mail client which kinda defeats the purpose of Apple Mail. Does anyone know what's happening with Apple updating the Mail app or have you figured a way to make this work properly? Many Thanks!