1) It would be useful if you can confirm that an email that is being edited is always an X00?
My understanding is that the message ID can be something other than X00 is the message hs been saved to the work in progress folder. However, X00 can still be used to access the message. See what MessageIDFromView() brings back. However, for confirmation you would need to ask Novell.
2) How does Groupwise know which message is the draft of the one being sent?
I suspect this must be internal GroupWise functionality.
More information might be available over in the Novell GroupWise developer Usenet forums: