When someone sends me an email and I open it, at that point I can read it but not write in it. Whenever I'm ready I can tell Outlook to reply to that message, and after that I can update its fields and hit <Send>.

I'm now writing a program that looks at the ActiveInspector and processes the email item. But how can my program tell whether that email item is modifiable or not—that is, whether or not the operator initiated a Reply before starting the program? There must be some status field in the inspector or the email item itself, but I can't find it.