This tutorial explains the steps required to transfers emails from Outlook 2011 folder to Mac Mail.
Step 1: Select the folder with emails on Outlook 2011 and move it to Mac desktop (or any other location). This should create .mbox file with folder name as the file name on your desktop.
Step 2: Now launch Mac mail, click the File menu and select Import Mailboxes from the menu list.
Step 3: In the Import screen, select Files in mbox format and click Continue button.
Step 4: Choose .mbox file which was created by moving the folder from Outlook 2011.
The following confirmation message would be displayed after successful import. The migrated folder with emails will be available on your Mac mail under Import section.