Tip - Implement TLS to Keep Your Email Secure

Email is the preferred method of communication for businesses. Still, it is effectively a plaintext communication sent from email clients to receiving email servers or from one server to another, leaving the content of messages in transit vulnerable to compromise without additional protection via encryption technology such as the Transport Layer Security (TLS) standard. Let’s explore TLS email encryption and how it helps secure email communications and protect the privacy of sensitive data.

What Is TLS Email Encryption?

Transport Layer Security (TLS) is a security protocol designed to provide privacy and data security over the Internet. It’s widely used in email, instant messaging, and voice-over IP applications. It’s also used in securing Hypertext Transfer Protocol Secure (HTTPS). HTTPS securely sends data from a web browser to a website. These remain the most publicly visible. 

As for emails, TLS protects email communication by establishing a secure and encrypted connection. This helps prevent unauthorized access to your email when it's in between Internet connections.

How Does TLS Help Secure Email Communications?

When an email is sent, TLS or SSL encrypts the connection from the sender's mail server to the recipient. This prevents unauthorized access and interception of the email content during transmission. It's important to note that TLS and SSL do not encrypt the email content; only the connection is encrypted. 

TLS Certificate Information for Exchange Online

Exchange Online always uses opportunistic TLS to encrypt connections with the most secure version of TLS. After that, it will work its way down the list of TLS ciphers until it finds one on which both parties agree.

If you decide to configure TLS between your organization and another trusted organization, Exchange Online can use forced TLS to create trusted communication channels. Forced TLS requires your partner’s organization to authenticate Exchange Online with a security certificate to email you. It’s important to note that your partner must manage their certificates. Exchange Online uses connectors to protect messages you send from unauthorized access before they arrive at the recipient's email provider. This ensures that your emails and accounts are protected. 

How Can I Set Up Forced TLS for Exchange Online in Microsoft 365?

To set up forced TLS for Exchange Online in Microsoft 365, it's necessary to create connectors. Connectors apply security restrictions to email exchanges between your organization and a partner organization or service provider. You can use transport layer security (TLS) to create a connector to enforce encryption. You can also apply other security restrictions like specifying domain names or IP address ranges from which your partner organization sends mail.

How Can I Check if an Email Is Using TLS?

If you’d like to know if an email uses TLS, some indicators will show it’s using it. Such indicators include: 

  • In the header, the receiver will log the encryption type and if one was used.
  • Keywords like “SSL,” “TLS,” and “Encryption” can be included in the display or in the encryption. Different email servers use different syntax and formats to show what encryption is used.
  • If you and your company use Microsoft 365, you must enforce TLS Exchange connectors. These are used to connect with your business partners or vendors. Also, in the TLS Exchange, you can use the built-in validation tool to ensure TLS works.

Keep Learning About Securing Business Email with TLS

You can read more at the Guardian Digital Blog about how TLS helps to secure email communications and how to configure TLS for the Postfix mail Transfer Agent (MTA), Microsoft 365 Exchange Online, and Google Workspace to help secure your email communications. 

Want to learn more about how to protect the privacy and security of your email with TLS? Get in Touch>>

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