Pretty sure the Outlook app is not free as they want you to buy it from the Microsoft website. My guess is when your subscription is up it will allow you to open to check old emails but will probably not accept new incoming mail or let you send.
Have you looked into the Apple Mail app crashing? That is not normal, I have had a few little things with Apple Mail but all in all I like the application. Only reason I use outlook now is because of work.
“If you are neutral in situations of injustice, you have chosen the side of the oppressor. If an elephant has its foot on the tail of a mouse and you say that you are neutral, the mouse will not appreciate your neutrality.” Bishop Desmond Tutu