Hi Andy,
I have tested this with the latest version of Office 2011 for Mac and an Office 365 after-upgrade account. However, I am not able to reproduce this issue. I suggest you refer to the following article to set up your email account.
http://help.outlook.com/en-us/140/gg471164.aspx
In addition, please check whether you have connection or access issue with Outlook Web App. If no, the issue may be caused by specific client configurations. We have professional support about Office 2011, you can post the question in that forum to resolve this issue. The forum address is provided as below.
http://answers.microsoft.com/en-us/mac/forum/macoffice2011-macoutlook?tm=1366201910402
Thanks,
Kevin Cui