Setting it up with an Office365.com company account is a little finicky. Here are the settings I used to get things working.
Username your full email address firstname.lastname@example.org
Incoming server: outlook.office365.com
Port: 993, Full TLS
Sending server: smtp.office365.com
Port: 587, TLS
Username: your full email address email@example.com
Password: your password
Then start enjoying your great new mail app!