First double check that the SMTP server does not require authentication to relay emails.
if you are still having the same problem, In the wWA_UniversalEmail/CDOSYS_VB.asp file, locate the following line:
retVal.Configuration.Fields("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
and change it to:
retVal.Configuration.Fields("http://schemas.microsoft.com/cdo/configuration/sendusing") = 1