Use the Priority property to change the message's priority. By default, the message's priority is Normal. The following sample shows how to send an high priority message:

Private Sub Form_Load()
    Dim m As Message
    Set m = Runtime1.NewMessage
    m.Priority = High
    If (0 = m.Send("me", "mike2@Unknown2.com", "Test", "Hello world!")) Then
        MsgBox "The message was delivered OK."
    End If
End Sub