Hi sjoshi ,
Thank you for your updates.
Based on my consulting, the attachment could be received in OWA but Outlook for Mac 2011 would be related to the relevant settings of Outlook for Mac 2011. In this situation, since there is the forum which is dedicated to the issues about Outlook client, it is recommended you contact Outlook for Mac forum to get a quicker response.
Your understanding is appreciated.
Thanks,
Edmond Peng