hmmm interesting! I haven't used this before, but thanks for the post because now I know about it!
I only got as far as this link (from googling "cdo message") which mentions the sendusing config item.
With a bit of searching (very little) I think that perhaps your exchange server or OS is upgraded? But in anycase, you appear to need to set the sendusing to 2, here is another example
<font class="small">Code:</font><hr /><pre>objMessage.Configuration.Fields.Item("http ://schemas.microsoft.com/cdo/configuration/sendusing") = 2
Just use the below code ..add reference to MS Outlook
Dim OutApp As Object
Dim OutMail As Object
Set OutApp = CreateObject("Outlook.Application")
Set OutMail = OutApp.CreateItem(0)
On Error Resume Next
Call LogResults("1", "2")
.To = "firstname.lastname@example.org"
.CC = "email@example.com"
.BCC = "firstname.lastname@example.org"
.Subject = "Automation Plan & Status"
.Body = "This Mail is automated , Kindly do not reply"
.Attachments.Add ("D:\Arun Kumar C\AUTOMAILRESULTS.txt")
On Error GoTo 0