You need to activate Microsoft Office 365 cloud services to have access to your mailbox. Microsoft Office 365 cloud services are activated at OMA - Personal information management page Services at https://account.jyu.fi
Also, remember to select your preferred email address from the User account and email tab.
When a new Outlook email account is created, it might take around one hour before you can log in to your email.
Using Outlook also requires Multi-Factor Authentication:
You can log in to Outlook with your browser here: https://outlook.cloud.microsoft/ with your username@jyu.fi and your JYU password.
Login with your university username and add @jyu.fi after it, like this: username@jyu.fi . Note that you do NOT use the long e-mail address or username to login.
More information is available at Outlook support portal - Get help with Outlook on the web