When a file that was created in Word, Excel, or PowerPoint is attached to an email message, personal information — such as your name or email address — might be added to the properties of the attached file. This information is primarily used by the Track Changes feature in Microsoft Office to identify who has made changes to the attachment.
If you do not use the Track Changes feature, you can prevent your personal information from being added to the properties of attachments, by doing the following:
On the File tab, click Options.
In the left pane, click Trust Center > Trust Center Settings.
In the left pane, click Attachment Handling.
Under Reply With Changes, clear the Add properties to attachments to enable Reply with Changes check box.