Hi Jean,
I have the same problem.
On my desktop I am using Outlook 2007 and on the laptop 2003. When I try to send email from 2007 to 2003 it doesn't work but it does work when I send them from 2003 to 2007 version. Also I have having my 2007 version crash constantly and don't know why. So I would be interested in hearing comments on this topic as well. Thanks for posting this thread.