Every message that is sent (over the Internet) has header information. This header contains all kinds of information regarding the message, where it comes from, sent to, time, message identifier etc. All mail servers use this information to process the messages.
But when you take a closer look you’ll see information in the header of a message about your internal network. For example, I’ve sent a message from my Hub Transport Server, throught my Edge Transport Server to an external recipient and this is what I seen in the header information: Continue reading Change SMTP Header Information