My hosting provider claims that this not to do with their mail server and offers the following statement:

"The "no such user here" error indicates that the sending process is not using SMTP-AUTH, which is required to send email to mailboxes that do not exist on that same server (which matches your other symptom). We're not intimately familiar with the mail sending functions of DNN, but based on your symptoms it would appear that the "single email" sending function and the "bulk email" sending function have two different areas to configure their SMTP settings... and that you do properly have SMTP-auth enabled for the single email feature, but do NOT have smpt-auth enabled for the bulk email sending feature. My recommendation would be to consult the relevant documentation or support for the DNN bulk email feature and find where the SMTP-auth settings are configured... and properly configure your smtp username and password in those settings."

I sure do think I have my host settings correct - It does send to local email addresses.  I does not send to email addresses off the hosting server.  is there another setting for Bulk Mail?

Thanks, Dan

Is there a seperate SMTP-Auth setting for the newsletter?  Why does the mail get sent induvidually but not when it is part of a bulk mail?

Also, everything works fine when I switch my host mail settings to another mail server - not at all associated with my hosting account.  This leads me to believe the problem is due to my hosting mail server settings.