A user asks: "When I send out a Word attachment it goes out as a 'read only' file. I do not designate the attachment as 'read only' and I have checked my security and the 'read only' button is not checked. This is driving me bonkers."

Your settings are not controlling the read only state of attachments sent to others, unless you specifically set a file to read only or otherwise locked it down to prevent editing.

The recipient's email program decides if the attachment should be read only. In Outlook opening as read only is "by design" when you open a file directly from the reading pane.

If you open the message then double click on the attachment, it should open normally.

Why the difference? In part so you are forced to save to document to save changes, because changes are more easily lost when you open messages from the preview pane.
http://www.outlook-tips.net/archives/20031002.htm