You cannot add attachments, delete or move many email messages in bulk in Outlook Web App

Consider the following scenario:

• You have the Microsoft Exchange Server 2013 Client Access Server role installed in a Microsoft Exchange Server 2010 environment.
• The Exchange Server 2013 Client Access Server role is published through a firewall or a proxy server, such as Microsoft Forefront Threat Management Gateway (TMG).
• You have a mailbox that is located on an Exchange Server 2010 Mailbox server.
• You log on the mailbox in Outlook Web App by using Internet Explorer 8, Internet Explorer 9, Internet Explorer 10, or Internet Explorer 11.
• Internet Explorer uses Microsoft Silverlight.

In this scenario, when you add many attachments to a new email message, the operation fails, and you receive the following error message:
When you perform a bulk deletion or a bulk move of email messages, the operation fails, and you receive the following error message:When you expand the report, the report is as follows:

To resolve this issue, install the following cumulative update:

These issues occur because the HTTP Proxy component on the Exchange Server 2013 Client Access server does not find the SOAP headers and the body for the requests. Therefore, the component cannot redirect the requests.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about how to publish Exchange Server 2013 by using TMG, go to the following Microsoft website: