Edit in Office using Office 2010 will change Mime Type to Text/XML - causing attachment download problem

Problem Description

'Edit in Office' feature using Office 2010 will change attachment's Mime Type to Text/XML - causing attachment download problem with the following error: error.png

How to replicate

1. Install Office 2010.
2. Attach an attachment: Excel or Doc or PPT. Note down the attachment Properties.
3. Edit in Office and save.
4. Notice the attachment properties has changed to Text/XML regardless what it was previously.
5. Try to download the attachment and the browser will refuse and show you an error.

Work around

Change attachment properties to what they were originally:

• XLS: application/vnd.ms-excel
• XLSX: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
• DOC: application/msword
• DOCX: application/vnd.openxmlformats-officedocument.wordprocessingml.document
• PPT: application/vnd.ms-powerpoint
• PPTX: application/vnd.openxmlformats-officedocument.presentationml.presentation