How to enable encryption in Gmail: a practical guide to TLS, S/MIME, and CLC

Protecting what you send via email isn't optional: it's essential. In Gmail, encryption adds a layer of privacy that shields your messages from prying eyes, both during transit and upon arrival. If you handle sensitive data, you should be well aware of the encryption options it offers. Google and how to activate them.

In this guide you will find, step by step, how Gmail security works, the differences between TLS, S/MIME and client-side encryption (CLC), how to activate them, how to check the protection level of each message and what alternatives to use if you work with other platforms or need extra features. The idea is that you can send emails with the peace of mind that only the intended recipient will read them..

Transport Layer Security (TLS): The foundation of encryption in Gmail

Gmail's first shield is TLS (Transport Layer Security), which is automatically applied to all emails you send or receive. Think of TLS as the “armored van” that transports your message between servers.

What does this mean in practice? If the recipient's provider also accepts TLS, the transmission is encrypted and you'll see a gray padlock icon indicating the standard encryption. The vast majority of modern email services already use TLS.

When the recipient's server does not support TLS, Gmail makes it clear: the message may be displayed with an open red padlock. In that case, avoid sending confidential information and Check for Gmail malfunctions or warns the sender or contact that your system does not encrypt in transit.

S/MIME in Gmail: Advanced protection for work and school accounts

For more demanding needs, Gmail supports S/MIME in Google Workspace (work and educational institutions). With S/MIME, each user has keys and certificates that allow them to encrypt and sign messages.so that only the authorized recipient can decrypt them.

Within S/MIME there are two ways to manage keys that should be distinguished: S/MIME hosted (Google securely retains a copy of the key) and Client-Side Encryption (CLC), where the organization exclusively controls the keys and not even Google can access the content.

The visual indicator also changes: messages with hosted S/MIME display a green padlock (enhanced encryption), while those protected with CLC are identified with a blue shield (additional encryption). Both options offer increased security compared to TLS, especially when the exchange is between users with S/MIME enabled..

How to check the security of an email in Gmail

Gmail allows you to check the "health" of each message in two situations. When writing, on a computer or AndroidYou can open the message security options. and see the level of protection available depending on the recipient.

When you receive an email, expand the sender's details to see the Security section. If an open red padlock appears, that message was not encrypted. and it is advisable to avoid responding with sensitive information and to inform the other party.

Enable and use S/MIME in Gmail (end user)

If you belong to an organization with Google Workspace and your admin has enabled S/MIME, using it is very simple. Compose the message as usual and, next to the recipient, click on the padlock. to check the available encryption level.

In View details you can select the highest level compatible with the recipient. The colors guide you: green (S/MIME), gray (TLS), and red (no encryption)Always bet on green when both parties have active S/MIME.

Enabling Client-Side Encryption (CLC) in Google Workspace: A guide for administrators

First of all, an important warning: CLC is not available on personal gmail.com accountsThis section is intended for administrators who manage domains for businesses, education, or other organizations.

The CLC can be activated by service and by organizational units (OUs) or configuration groups. It is recommended to enable it only for users who need to create or manage encrypted content in each product:

• Google Drive: for those who create Documents, Sheets or Presentations with CLC or upload encrypted files.
• gmail: for those who send and receive encrypted messages on the client side.
• Google CalendarFor users who generate encrypted events. If they will be attaching CLC files or scheduling encrypted meetings, also enable CLC in Drive and Meet.
• Google MeetFor those organizing meetings with CLC. It does not need to be enabled for other attendees.

Users who only need to read or edit encrypted content do not require full CLC activation to create. It is sufficient that their access allows them to view or collaborate on content that is already encrypted..

Steps to activate or deactivate CLC by service, OU or group (super administrator role): access the console and go to Menu Data > Compliance > Client-side encryption.

In Applications, choose the service (Drive, Gmail, Calendar, or Meet). From here, you can also go to "Encryption with external key service" or "Encryption with hardware keys" and click Assign; then, under "Encryption by application," select the desired service. In the left panel, select the OU or group. where you will apply the change.

In Client Encryption Status, select Enabled or Disabled and confirm in the pop-up window. If you need users to send CLC emails to recipients without S/MIMEIn Gmail, activate "Encryption with guest accounts" (requires the Assured Controls or Assured Controls Plus add-on).

Optionally, you can force encryption to be enabled by default in Gmail, Drive, or Calendar on the web and apps mobiles by selecting “Enable client-side encryption by default” for the OU. This preconfiguration also requires Assured Controls or Assured Controls PlusUsers will still be able to disable encryption on a case-by-case basis.

In environments with policy inheritance, use Override to maintain your setting if the parent OU changes. If the status was already Cancelled, you can choose to Inherit or Save to retain the new setting even if higher-level policies change.

Keep in mind that changes can take up to 24 hours to spread, although they usually take effect sooner. If you need more information, consult the Google Workspace administration documentation..

If you already activated CLC in Gmail: S/MIME certificates and metadata

When you can't use "Guest account encryption" for Gmail after enabling CLC, It is necessary to prepare and upload the S/MIME certificates and the metadata of the encrypted private keys. of each user who will work with CLC in Gmail.

This step ensures that the ecosystem of keys and certificates is ready to securely encrypt and decrypt messages. Consult the specific guide for “Setting up Gmail CLC for users” to perform the charge correctly.

Troubleshooting CLC

If your users report errors when sending or receiving with CLC, go to the Alerts Center in your console. There you will see incidents and diagnostics related to the client-side encryption service. that will help you locate the fault and act quickly.

Gmail's confidential mode: useful, but not a substitute for encryption

Do you use a free account and want to add extra control? Confidential mode limits actions such as forwarding, copying, printing, or downloading, allows you to set an expiration date, and requests an SMS code. Remember: it's not end-to-end encryption.

To send a confidential message: compose the email, activate confidential mode, choose an expiration date, and, if you wish, request SMS verification by indicating the recipient's number. The content will remain visible in your Sent folder and the recipient could take screenshots.So don't treat it as real encryption.

Configure secure SMTP (TLS/SSL) sending in Gmail's "Send as" settings

If you've noticed errors when sending from accounts configured in "Send as", it may be due to stricter TLS requirements in SMTP. Review and update the settings to SSL/secure port in Gmail.

Summary steps: Access Gmail from your browser (see How to configure IMAP, POP and SMTP email), open Settings > Accounts and Import, locate the address in “Send as” and tap Edit details. In the SMTP section, enter the secure server. (for example, domain-example-com.securemail.dinaserver.com), port 465 and check the SSL box.

Save changes and try again. With this configuration, your transmissions will continue to meet TLS/SSL security requirements and you will avoid mistakes due to stricter recent policies.

What is email encryption and how does it work?

Encryption turns the readable text of an email into unintelligible data that can only be reversed with the correct key. It is based on public-key cryptographywhere each user has a public key (for encryption) and a private key (for decryption).

Certification authorities issue digital certificates that link public keys to verified identities. This allows for authenticity and trust when exchanging encrypted messagesAlgorithms such as RSA are common in these schemes.

Furthermore, it is important to distinguish between encryption in transit (protects while the message is traveling) and encryption at rest (protects when it is stored). The combination of both significantly reduces the attack surface.

Secure email protocols: S/MIME and PGP/MIME

S / MIME It uses an infrastructure with certification authorities to manage identity and algorithms. It is integrated into iOSIt is compatible with macOS and Gmail and Outlook, so its adoption is very widespread in corporate environments. Requires valid certificates for each user.

PGP/MIMEWeb of Trust, on the other hand, operates with a more decentralized trust model. It is flexible and gives the user greater control, but it often requires third-party tools, as many services do not include it by default. If you're looking for complete control and end-to-end encryption, PGP/MIME is a solid choice..

Encrypt email on other platforms and devices

Outlook It also supports S/MIME and you can configure Outlook To use it, you must obtain the digital certificate/ID, install the S/MIME control, and, from the settings, decide whether to use default encryption or digital signatures. For individual emails, use “more options” and enable “Encrypt this message (S/MIME)”If the recipient does not have S/MIME, they may not be able to read the email.

En iPhone (IOS) S/MIME support is included. Activate it in Settings > Mail > Accounts > Advanced, and enable “Encrypt by default”. When composing, you'll see a padlock next to the recipient that must appear closed for the message to be sent encrypted..

En AndroidS/MIME or PGP/MIME encryption usually requires third-party apps. If you use Gmail and have S/MIME enabled in Workspace, you can benefit on any device. when working in the corporate ecosystem.

Other platforms like Yahoo or AOL They do not include native S/MIME in all cases, and will need plugins to handle PGP/MIME or S/MIME. The general rule: if your provider doesn't integrate the protocol, install a proven third-party solution..

Tools and services to strengthen email encryption

• CipherMail It stands out for its versatility: it allows encryption with S/MIME, OpenPGP, TLS and PDFIt offers free open-source editing and paid options. It's especially popular on Android..
• Mailvelope It works as a browser extension (Chrome, Firefox, Edge) and encrypts with OpenPGP on web providers such as Gmail, Outlook, or Yahoo. The project is open source and its basic extension is free..
• Virtru It integrates seamlessly with Gmail and Outlook and supports the open standard TDF (Trusted Data Format). In addition to encryption, it adds controls such as watermarks and persistent permissions for attachments. It is simple for the user because it hosts and manages the key exchange..
• Lockmagic It offers a Gmail extension that makes it easy to encrypt emails, set expiration dates, and apply an identity-based client-side encryption model. Its passwordless operation reduces friction for the end user..
• Start email It supports PGP and integrates with services like Outlook or Gmail. It offers paid and free plans according to your needs.
• send 2.0 It promises robust “military-grade” encryption and is compatible with Outlook and Gmail via a plugin. It includes different plans to suit different scenarios.
• Enlocked It allows you to send and receive PGP-encrypted email in Gmail, Yahoo, AOL, Microsoft and Outlook, with a Chrome extension. Offers free and paid options.

How to tell if a Gmail email is encrypted (icons and colors)

To check a received message, open it and tap the arrow next to the sender's name to see the details. In the Security section you will see the type of encryption applied.

• Green: message protected with S/MIME (it can only be decrypted with the recipient's private key).
• Grey: protected using standard TLS (works if both servers support TLS).
• RedThe email was sent without encryption.

If you are writing, you can also click on the padlock and on "View details" to check the available level and, if necessary, raise it. Always give preference to the highest compatible level between transmitter and receiver..

There's a lot of talk about numbers, and it's no coincidence: much of Gmail's traffic travels encrypted by default with TLS, and organizations can raise the bar with S/MIME and CLC. With all of the above, you now have a clear roadmap to activate, verify, and optimize encryption in Gmail.Whether you use a personal account with confidential mode or manage a Google Workspace domain with S/MIME and CLC properly configured.

Related article:

Comparison: Google Workspace vs. Microsoft 365 for collaboration and security

Isaac

Passionate writer about the world of bytes and technology in general. I love sharing my knowledge through writing, and that's what I'll do on this blog, show you all the most interesting things about gadgets, software, hardware, tech trends, and more. My goal is to help you navigate the digital world in a simple and entertaining way.