There are three sets of servers involved in this example: one machine at Hotmail, one machine at Proofpoint, where our Premium Email Filtering takes place, and some machines at LuxSci, where final acceptance of the message and subsequent delivery happened.Each Received line documents what a server did and when.The first one listed shows the last server that touched the message the last one is the first server that touched it.

They are in reverse chronological order.The things to notice about these Received headers are: Mon, 07:41:19 -0700 What do These Received Headers Say? The email addresses, IPs, and other information are fake for obvious reasons. If you look at the “source” of the email message, the lines at the top start with “ Received.” In an example email message from someone on Hotmail, the Received headers look like this. To determine if the message was transmitted between the sender’s and recipient’s servers securely (over TLS), we need to extract the “Received” header lines from the received email message. The intermediate step, where the email is transmitted between two different providers, is where messages may be insecurely transmitted. Indeed, most users who need to can take steps to ensure that they are using SSL-enabled WebMail or POP/ IMAP/ SMTP/Exchange services so that steps 1 and 3 are indeed secure. It is step 2 that people are most concerned about they usually assume or check that everything is secure and OK at the two ends. Finally, the recipient downloads the message from their email server.The sender’s email or WebMail server then talks to the recipient’s inbound email server and transmits the message to them.The sender’s computer talks to the sender’s email or WebMail server to upload the message.An Example Email Messageįirst, we must understand that an email message typically passes through several machines on its way from sender to recipient. Hotmail is not a good provider to use when security or privacy are required. We will see that Hotmail did not use TLS when sending this message. To analyze a message for transmission security, we will look at an example email message sent from Hotmail to LuxSci. It is actually easier to tell if a recipient’s server supports TLS than to tell if a particular message was securely transmitted. However, it requires some knowledge and experience to understand the text. To see if a message was sent securely, looking at the raw headers of the email message in question is easy. For example, banks, healthcare organizations under HIPAA, and other security-aware institutions require that emails be secured by TLS encryption.Įmail should always be transmitted with this basic level of email encryption to ensure that the email message content cannot be eavesdropped upon. Frequently, we are asked to verify if a sent or received email was encrypted using SMTP TLS during transmission.

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