Hi, and thanks for reading

I writing an small email app in VB6, with Groupwise 5 as the default mail client. I am constructing emails with the MAPIMessage and MAPISession Controls in the normal fashion as can be seen in any number of books The problem I'm having is a strange one :-
When Sending Internet Mail with "MAPIMessage.RecipAddress = "Internet:[email protected]", when we get to MAPIMessage.Send, I received a "<post office> undeliverable for <message subject>" in my inbox. Fair enough, you might think.
But when I use "MAPIMESSAGE.Send True", the UI appears with all information present, and when we Click "Send", we are invited to the Address book to resolve the name "Internet:[email protected]". However, if we click on the crossed-out "internet:[email protected]" from the dropdown list that appear under the "To:" text box, the message is delivered.
This bizarre behaviour is completely reproducable, and most disconcerting. Groupwise continues to reject the supllied address until it is manually selected from the list (whether or not it has been Crossed out by groupwise already). The practical result as far as I'm concerned, of course, is that when .Send is used with no UI, the message just does not depart.

What the hell is going on?
Has anyone experienced similar behaviour?
Has anyone successfully programmed a vb app to send emails over Groupwise?
Help...?

thanking you for your wossname,

surrendermonkey