When it comes to transmitting sensitive information, email security is a priority, whether you’re a business or a consumer.
TLS email encryption has become a vital part of keeping data safe in transit, shielding it against potential interception.
Let’s explore how TLS email encryption works, what it offers, and how you can set it up.
TLS stands for Transport Layer Security.
It’s a protocol that protects data as it travels between systems, such as websites or email servers.
TLS replaced the older SSL (Secure Sockets Layer).
It helps stop unauthorised parties from reading data as it moves across networks.
When you use TLS for email, you add two important security layers.
TLS sets up a protected connection between email servers, keeping messages safe as they travel.
The encryption process has a few steps:
TLS is good for stopping unauthorised access to emails while they move from one server to another.
It doesn’t offer end-to-end encryption (covering messages throughout their journey), but it helps solve a few email security problems.
Man-in-the-middle attacks are a global threat.
These attacks happen when a malicious actor intercepts and potentially alters the communication between two parties without their knowledge.
TLS makes emails unreadable during transmission.
TLS adds a layer of security to regular email exchanges, helping guard information that’s not highly sensitive but still private.
If you must meet data regulations, like those from the ICO or GDPR, TLS can help you stay compliant.
You might need stronger encryption to fully protect very sensitive data.
TLS lowers the chance of data leaks between email servers by protecting information in transit.
Devices and systems at either end may still be weak spots, but TLS covers the path between them.
TLS is mostly handled by the email server, so users rarely need to do anything.
It scales well and suits consumers and businesses of all sizes.
TLS has many plus points, but there are limits.
TLS protects emails in motion between servers.
But it’s not true end-to-end encryption.
Once the email reaches the recipient’s server, it’s no longer encrypted.
If the recipient’s server doesn’t support TLS, a message may be sent in plain text (depending on the email provider).
For this reason, many use other encryption methods in combination with TLS to ensure protection throughout message transfers.
"TLS encryption is an effective measure for securing data during transmission, but it does not address vulnerabilities at either end of the communication."
– Mike Wakefield, CTO, Beyond Encryption
TLS is often easier to set up than some end-to-end encryption methods because it works at the server level.
Here’s a quick guide:
Most email services, such as Microsoft 365, Gmail, and Exchange, support TLS natively.
But check that both your and the recipient’s servers have TLS enabled.
Configuring your server for TLS is important.
Usually, you can easily configure the settings to require TLS for inbound and outbound mail.
Set a policy that requires TLS for all emails containing sensitive information.
Explain what to do if TLS isn’t available.
Check your email server logs to make sure TLS is running smoothly.
Look for any unencrypted emails to review and address errors.
TLS encryption protects emails between servers, but your needs may go further – especially if you are in a regulated sector.
If your company deals with highly sensitive data, such as financial or medical records, TLS alone might not do the job:
If the recipient’s server is compromised, the data could be at risk.
Consider stricter rules in industries like healthcare, finance, or law.
TLS helps with compliance, but many regulations suggest end-to-end encryption and other safeguards.
"For everyday communication, TLS alone may provide a reasonable level of security.
However, organisations should assess whether it’s sufficient for sensitive data or compliance requirements."
– Paul Holland, Founder, Beyond Encryption
TLS is useful, but other methods might be better for certain needs.
Let’s take a quick look.
S/MIME is a trusted encryption standard with digital signature support.
It encrypts the email’s content at the message level, so it stays protected even after it reaches the inbox.
Digital signatures confirm the sender’s identity and show if anyone has tampered with the message.
Pros:
Cons:
PGP also offers encryption and digital signatures, but it uses a decentralised ‘web of trust’ instead of central certificate authorities.
Users create and manage their own keys, then build trust directly with others.
Pros:
Cons:
E2EE makes sure only the sender and the recipient can see the email’s contents.
It encrypts messages on the sender’s device and only decrypts them on the recipient’s device.
This means the message stays secure throughout its journey.
Pros:
E2EE is a top choice for sensitive data, like financial or medical records.
Tools like our own secure email solution, Mailock, add features such as recipient verification, which keeps data extra safe.
TLS is a widely supported way to secure email data while it’s in transit.
It offers good protection from interception, eavesdropping, and data theft.
It can help organisations meet basic security requirements, and it may support some compliance needs.
However, TLS isn’t end-to-end, and it relies on the recipient’s server supporting TLS.
Companies that handle highly sensitive data might consider S/MIME, PGP, or an E2EE secure email solution like Mailock.
Most modern email providers support TLS by default, including Gmail and Outlook.
If the other person’s server doesn’t support TLS, your message might end up unencrypted.
You can switch on TLS by installing a valid digital certificate and requiring TLS for inbound and outbound mail.
Many hosting providers have built-in tools for this.
Look in your email headers for a note on TLS.
Some clients show a padlock icon when TLS is active.
TLS encrypts mail between servers only.
It doesn’t protect data once it’s on the recipient’s server.
If that server doesn’t support TLS, your email goes in plain text.
TLS secures the path between servers.
End-to-end encryption covers the entire journey from your device to the recipient’s, so nobody else can read it.
How To Prevent Man-In-The-Middle Attacks, Cybernews, 2025
Google Transparency Report, Google, 2025
Sam Kendall, 23.01.2025
Sabrina McClune, 23.01.2025