How to change email body in a newly created exchange.data.transport.email.emailmessage

I had created an exchange transport agent for manipulating incoming email to our exchange 2010 server.
One of its functions is to alert some users, by email, for an email received under specific conditions. So i wrote a code that creates a new email message and saves it in the Pickup folder of the "transportroles", which is working perfectly. However I can not find the way to add/change the body of it since it is read only.
Here is the code:
Public Sub SaveEmailForSend(ByVal FromEmail As String, ByVal TheSubject As String, ByVal theBody As String, ByVal ToEmails As String, Optional ByVal CCEmails As String = "", Optional ByVal BccEmails As String = "", Optional ByVal AttachEmail As EndOfDataEventArgs = Nothing, Optional ByVal FileName As String = "NewEmailToSend")
         
  Dim newEmail As EmailMessage = EmailMessage.Create(BodyFormat.Html)
            Try
                newEmail.From = New EmailRecipient("", FromEmail)
                newEmail.Subject = TheSubject
                ' HERE IS THE PROBLEM
                newEmail.body = TheBody
                ' end of HERE IS THE PROBLEM
                If Not ToEmails Is Nothing Then
                    For Each ToRec In Split(ToEmails, ";")
                        newEmail.To.Add(New EmailRecipient("", ToRec))
                    Next
                End If
                If Not CCEmails Is Nothing Then
                    For Each CCRec In Split(CCEmails, ";")
                        newEmail.Cc.Add(New EmailRecipient("", CCRec))
                    Next
                End If
                If Not BccEmails Is Nothing Then
                    For Each bccRec In Split(BccEmails, ";")
                        newEmail.Bcc.Add(New EmailRecipient("", bccRec))
                    Next
                End If
                If Not AttachEmail Is Nothing Then
                    Dim Attach As Attachment = newEmail.Attachments.Add("RejectedMessage", "message/rfc822")
                    Attach.EmbeddedMessage = AttachEmail.MailItem.Message
                End If
                Dim file As FileStream = New FileStream(reg_SERVER_PICKUP_DIR & FileName & ".eml", FileMode.Create)
                newEmail.MimeDocument.WriteTo(file)
                file.Close()
            Catch e As Exception
                WriteEventLog(e, ErrLevel)
            End Try
        End Sub