Where did all my Outlook mail go?
First, all your emails are still in your web version of MSN.

You need to switch the MSN to IMAP type and it is called Outlook (the web version) of Outlook, not the office version.

In your Mac Mail set up following:

Choose Account Type: IMAP.

Input the following as the Incoming Mail Server: imap-mail.outlook.com.

Choose to Use Secure Sockets Layer (SSL) for incoming mail security.

Input the following as the Outgoing Mail Server: smtp-mail.outlook.com.

Choose to Use Authentication.

Choose to Use Secure Sockets Layer (SSL) for outgoing mail security.

Depending how large your mail is it might take a while to transfer. To monitor the process turn on the Activity, located under the Window Tab in Mail app.