this is a nice refrence
http://www.madboa.com/geek/sendmail-auth/
I maed the change in the sasld mechanism per his directions and now that user can send email. Not sure why the other could....
my apologies, this was not an ISPConfig issue.
So far it is working nicely for me. The GUI is not as comfortable as compared to my cobalt raq...but it had a team of developers. And this package is significantly easier to track down what is going on.