Sometimes messages created by an application using simple MAPI and displayed by Outlook do not send when the send button is clicked. The button depresses as it has been clicked by the message does not go - the dialog stays there. Often repeated clicking sends it but not always.
Occasionally this occurs when the message has been created with the Outlook new message option.
The messages sometimes get saved to the Inbox rather than the Draft folder.
Problem observed with Outlook 2002 and 2003.