If you need to move emails from an MBOX archive file, start here to import that file. Otherwise, proceed to Setting up Exchange
These step-by-step instructions were created by modifying and adding screenshots to this post, which is recommended as a summary of the process.

Importing MBOX files

1. In your Mail, select “File” >> “Import Mailboxes”
   
2. Choose to import “Files in mbox format”, then click “Continue”
   
3. Select your mbox file, and click “Choose”. DO NOT click on the contents of the mbox file.
   
4. Your emails will be saved in a folder named “Import”. You’ll need to come back here in a future step.
   

Setting up Exchange

1. In your Mail app, click the “Mail” tab and choose “Add Account”.
   
2. Choose to make an Exchange account, then click “Continue”.
   
3. Enter your name followed by your WSU email address.
   
4. Choose “Sign In”.
   
5. Sign in with your WSU account.
   
6. You should now have a set of mailboxes labelled “Exchange”.

Moving Emails to Exchange

Be aware that if you have a lot of emails, this process will take a long time.

1. Create a new mailbox in your “Exchange” set of folders. I named mine “MacInbox”.
   
2. Select all the mails you wish to move to Outlook. If you imported an MBOX file, these will in the “Import” folder we created earlier. Drag them into the new mailbox you created in the Exchange account.
   
3. Your emails will now begin syncing to your Outlook (WSU) account.
   

Making an Outlook PST backup

If you want to make a backup or an archive of the emails you just imported, you can follow these instructions to create an Outlook PST file.