Hi Pinbot,
To troubleshoot the issue, please follow the steps below.
1. Please make sure the Outlook 2011 for Mac is updated to the new version.
2. After you make the change in Outlook 2011 for Mac, please log in to the OWA (Outlook Web App) http://mail.office365.com/ and check whether the change you did exist.
3. Please click on the link below to troubleshoot the issue.
http://support.microsoft.com/kb/2360509
Thanks,
Yang Yu