Assume that you have a Microsoft Exchange Server 2010 Edge Transport server that has the Attachment Filter agent enabled. A user outside your organization sends you an email message that contains a Microsoft Office file type attachment, such as .docx, .xlsx, .xls and so on. In this situation, the attachment is removed unexpectedly when you receive the email message.
This issue occurs because the Edge Transport Attachment Filter agent incorrectly considers the attachment as an invalid file, and then removes it.
To resolve this issue, install the following update rollup:
2803727 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 3
To work around this issue, use one of the following methods.
Run the following cmdlet to disable the Attachment Filter agent on the Edge Transport server:
Add the following key between the <appSettings> element and the </appSettings> element of the EdgeTransport.exe.config file:
<add key="AllowInvalidAttachment" value="true" />
Restart the Transport service.
Verify that this issue is resolved. To do this, send an email message together with an attachment that contains the affected file type. Make sure that this email message is processed correctly by using the updated Edge Transport server.
Note If the AllowInvalidZipInAttachmentFilterAgent key is also set in the EdgeTransport.exe.config file, the AllowInvalidZipInAttachmentFilterAgent key takes precedence over the AllowInvalidAttachment key.
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 configure the attachment filtering, go to the following Microsoft website: