You may be able to handle the ValueChanged event and modify the MessageBody property like this to insert values:
Private Sub Emailer1_ValueChanged(sender As Object, e As EventArgs) Handles Emailer1.ValueChanged
Emailer1.MessageBody = "Current Value=" & EthernetIPforCLXCom1.Read("MyTag")
End Sub
The initial send is caused by the control not knowing the existing value, so when it starts up, it can only assume the value changed. In the upcoming Beta 35, there will be a fix to prevent this.