Can't change .UnRead property on an unsent mail item

[James]

I can't seem to change the .UnRead property of a unsent mail item to false.
I can change it on received mail items.

I'm creating mail items with attachments from an ftp-like server for the
user to see in their Inbox. It is very desirable to mark some of these
messages as read I create them for the first time and some of them new.

I experimented by placing some code in a timer method to change the .UnRead
property of all items in the Inbox. Those mail items that I had created
which were unsent were unaffected by the timer method while everything else
was.

Is there a trick to getting unsent mail items (with file attachments) to
look like they have been read?

Thanks,
James