Exchange 2013 CU6 - Mail Enabled Public Folders reject emails externally with a NDR

Users who send emails to a Mail Enabled Public Folder see an NDR when emailing externally even though the folder is set to allow emails without authentication.

NDR after CU6

When you send an email to the Mail Enabled Publci Folder post CU6 you will receive an NDR such as the above.

Exchange CU6 Update Notes

The change to the security is explained in the Exchane 2013 CU6 Notes here

Add Anonymous Permissions

To allow emails to be sent to the folder you can use the above Power Shell to enable Anonymous CreateItems permission on the folder.
Add-PublicFolderClientPermission "\Customer Feedback" -AccessRights CreateItems -User Anonymous