TLS for Email: What Is It and How Can I Tell if an Email Has It?

Transport Layer Security (TLS) is an encryption protocol used to protect email messages between sender and recipient, preventing eavesdroppers from reading your messages.

In this article, you will learn about Transport Layer Security (TLS), how it works, why you need it, and how to ensure your emails are correctly encrypted.


What Is TLS?

TLS is a common internet security protocol that is used to enable secure internet conversations that provide both privacy and data protection. TLS was created by the Internet Engineering Task Force (IETF), and its first version was released in 1999.

TLS evolved from the Secure Sockets Layer, or SSL, encryption mechanism. Because the two protocols are so closely connected, you may hear people use the terms SSL and TLS interchangeably to describe secure internet interactions.


Secure connections are typically established using ports 587, 2525, and 465. These ports may differ depending on whether you use IMAP or POP3 to access your server’s emails. Your system administrator may also configure mail servers and other apps to use certain ports for encryption.



The protocol instruction STARTTLS is used to notify an email server that the client intends to upgrade the connection from an unsecured to a secure one. 


STARTTLS can secure an unsafe connection using the TLS protocol. When you enable this option on your mail server, a secure connection is created before any emails are transmitted.


Role of TLS in Protecting Email exchanges

TLS contributes to the security of email exchanges by establishing a secure and encrypted connection between two sites. TLS employs asymmetric encryption to ensure that email conversations remain private and unaltered while in transit. Encrypting emails guarantees that the contents of the message cannot be read or modified while being delivered, and it also serves as a tool for authentication between the sender and the receiver.

Emails sent using SMTP without encryption are vulnerable to man-in-the-middle attacks or wiretaps. These attacks have the ability to quietly copy your emails and read their contents, as well as modify the contents of the message while en route. This not only jeopardizes the email’s integrity but also exposes important information to attackers looking to conduct even more complex assaults against it.


A TLS handshake is a set of processes that are used to create secure connections. This handshake necessitates the participation of two people in order to establish a secure connection. The handshake procedure begins when a message is transmitted via TLS.


  • The client and server will indicate the version of TLS they will use for the session during the initial step of the handshake.
  • The client and server will choose the encryption suite to employ.
  • The server’s identity will be verified using the server’s TLS certificate.
  • Once the handshake is complete, session keys will be produced and used to encrypt the email communications.


Steps to Check TLS Implementation 

Today about 90% of emails, both sent and received, are encrypted. But how can you know that for sure?

Server admins should be able to confirm that their email server is employing encryption by checking their certificate store and ensuring that their certificate is both appropriately installed and up-to-date.

If you’re only checking an email, you may inspect the message’s headers to see if it was transmitted using encryption. In Gmail, open the email in question and click on the tiny arrow next to your name beneath the sender’s address.


In Microsoft Outlook, you can do this by opening the email you wish to verify and then navigating to ‘File’ > ‘Properties’. This will display the email header information, including any TLS information if it exists.


Is TLS Enough?

The simple answer is NO. TLS cannot protect emails against phishing attempts that use lookalike domains, malicious attachments that contain viruses, email links that redirect to phishing sites, social engineered emails that trick recipients into sharing sensitive information, and servers sending spoof emails from domains they do not control. 


So what else do you need…? Us. 


Yes, you read that right. We, at EmailAuth, provide Email security solutions including DMARC checker, DKIM checker, SPF checker, and other email authentication services. DMARC for your emails ensures that your emails are sent from verified domains that cannot be spoofed or phished. Get DMARC here today!


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