If you send Simple Mail Transfer Protocol (SMTP) mail by using a Collaboration Data Objects for Windows (CDOSYS) application, a Collaboration Data Objects for Exchange 2000 (CDOEX) application, or System.Web.Mail on a computer where Exchange 2000 Server Service Pack 3 (SP3) is installed, you receive the following error message:
CDO.Message.1 (0x80040220)
The "SendUsing" configuration value is invalid.
http://support.microsoft.com/default.aspx?scid=kb;en-us;816789