I think the value of the sendusing field is incorrect, try this...
Code:
.Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2 ' send using port
.Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = <smtp address>
.Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
HTH,
Chris