Answered my own question. For those with a similar issue, it seems you
need to specify a few additional things:

objNewMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
objNewMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/smtpserver") = _
"myserverl"
objNewMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
objNewMail.Configuration.Fields.Update

Details can be found at:
http://www.microsoft.com/technet/scr..._ent_wbpa.mspx