the code  I'm using :
always "invalid value of sendusing" error eccuring...
I turned the code to smtp now, but I think this way is faster (if it
works :)

Dim oMessage As New CDO.Message()
'Create a Message Object
oMessage = CreateObject("CDO.Message")

With oMessage
'Set the properties
.To = "burciny@..."
.From = "burciny@..."
.TextBody = "This is a sample Body" 'Your TextBody
.Subject = "This is a sample Subject" 'Your Subject
.Configuration.Fields("CdoSendUsing").Value =
CdoSendUsing.cdoSendUsingExchange
.Configuration.Fields.Update()