Hmm. There are millions of possible reasons, may I suggest that
you start by disabling MIME on your Emailer configurations and
see if it helps.
Now John and Cynthyia should contact the postmaster or support
division of your ISP and ask for them to check the error log for
more detailed cause of the problem
Contact me directly off list for further investigation...
Dr. E. Aspler
Ganoksin Jewelry Co.,Ltd.