How to encrypt email? Email encryption is the process of scrambling and disguising the contents of an email so that only the intended recipient can read it. Encoding the content of sensitive emails prevents the compromise of information. So, even if a threat actor gets their hands on critical details, email encryption won’t allow them to decode, understand, and misuse them for attempting malicious activities. It is a way to protect your emails from being intercepted by people who might want to steal sensitive information, such as passwords or personal details. It is also useful if your employer wants to see all of your emails and you want them to be private. The increased number of phishing attacks, data breaches, BEC scams, and other types of cybercrimes have fueled the need for enterprises, government bodies, and individuals to exchange encrypted emails. Considering the rapidly growing cyber menace, regulatory bodies across the globe have laid down stringent mandates, including email encryption. Both of these factors are pushing companies and individuals to adopt security measures to shield emails’ content.

Key Takeaways

Email encryption protects sensitive personal and corporate information from unauthorized access and data breaches, ensuring only the intended recipient can read the message.
Adoption is driven by increasing cyber threats (phishing, BEC) and is essential for regulatory compliance (e.g., HIPAA, GDPR), preventing significant fines and reputational damage.
Key methods include end-to-end encryption like PGP and S/MIME (often using asymmetric keys) and transport encryption like TLS (enforced by MTA-STS) to secure emails during transit between servers.
Encryption prevents unauthorized message modification and sender impersonation, safeguarding message integrity and trust in communications.
While distinct from email authentication (like DMARC), email encryption complements it, providing comprehensive security by protecting content confidentiality alongside verifying sender identity.

What is email encryption?

Encryption is the process of encoding a message in such a way that only authorized users have the ability to read it. Email encryption specifically involves barring hackers and other unauthorized people from reading the content of email messages you send by disarranging the message into an incomprehensible format. The goal of email encryption is to make sure that your emails are safe from prying eyes and can only be read by those you trust. The encrypted emails can then be decoded only at the desired recipients’ ends.

Email encryption is important because it protects your personal information and helps prevent your email address from being abused. If someone wants to steal your personal information or harass you, they can use an email address like yours without worrying about getting caught. Emails are the basis of corporate communication, meaning that a lot of sensitive and secretive company information along with personally identifiable data are exchanged daily. Data leaks are a common threat plaguing email communications, leading to devastating breaches of corporate data, files, financial information, and employee details. This makes email encryption a vital method for protecting email data and mitigating the risks and costs associated with breaches, including legal fees, regulatory fines, and reputational damage. Furthermore, encrypted communications enhance trust among clients and business partners.

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The process of email encryption

When you send an email message, it goes through multiple steps in order to ensure that only the intended recipient can read it. The first step is called “encryption,” and it scrambles your message so that only someone who has access to the right key can decrypt it. Email encryption can be facilitated by installing encryption software on your device, however, more recently, cloud-based hosted solutions and platforms facilitate email encryption without needing to install applications, offering better efficiency. The process can either be automated, encrypting all outgoing email traffic, or manual, encrypting only specific messages containing sensitive information.

The second step is called “decryption,” and it allows recipients to retrieve their original messages without having to go through encryption steps first—they just need to know where their keys are stored so they can retrieve their own messages from there. Two primary methods underpin most email encryption protocols: Symmetric Encryption, where the same key is used for both encryption and decryption (requiring secure key sharing), and Asymmetric (or Public-key) Encryption, which uses a pair of keys – a public key shared openly for encryption, and a private key kept secret by the recipient for decryption. Asymmetric encryption is generally considered more secure for key distribution.

How to encrypt email: The various types of email encryption

1. S/MIME email encryption

S/MIME stands for Secure/Multipurpose Internet Mail Extensions. It’s a widely supported standard for public key encryption and digital signing of email content. It’s useful for sensitive data like credit card numbers, Social Security numbers, and bank account info, requiring the issuance of digital certificates from a reliable Certificate Authority (CA) to verify identities.

This process involves two parts: one part where the message is encrypted using the recipient’s public key and potentially digitally signed using the sender’s private key, and another part where it is decrypted using the recipient’s private key and the signature is verified using the sender’s public key. The encryption happens before the recipient receives it; then they decrypt it before reading it. This keeps them from seeing any private data or information that might be included in your email.

You can send S/MIME encrypted emails using many popular email clients—including Gmail and Outlook—or by using apps like Thunderbird or Apple Mail if you have an iPhone or iPad, provided certificates are properly configured.

2. PGP email encryption

PGP (Pretty Good Privacy) — This is another well-known standard for email encryption, often favored by activists, journalists, and individuals prioritizing privacy, as well as corporations seeking robust security. It uses a combination of symmetric-key and public-key encryption.

PGP works by creating a digital signature on each message and encrypting it, typically using a system where users generate their own key pairs and exchange public keys through a web of trust or key servers, rather than relying solely on centralized CAs like S/MIME.

It was developed by Philip R. Zimmermann in 1991. Using this encryption method, any message can only be read by someone who has access to the recipient’s private key and potentially knows the secret passphrase that unlocks that key. That makes it extremely secure—even if someone intercepts the message, they won’t be able to read it without the correct private key.

3. Transport Layer Security (TLS)

Transport Layer Security, or TLS, is a protocol used to encrypt communications between email servers (and between clients and servers). It’s the successor to SSL and is also used when you connect to a website using HTTPS.

What does this mean for email encryption? When you’re sending an email, TLS encrypts the connection between the sending mail server and the receiving mail server, protecting your message from being read by anyone who intercepts it as it travels through the internet. This helps protect your messages from getting intercepted by hackers or surveillance agencies during transit. Major mailbox providers like Gmail support TLS encryption but often require the receiving server to also support it.

But what if someone steals your phone or computer, or compromises the mail server itself? TLS only protects emails while they’re *in transit* between servers. It does not typically encrypt the email on the servers or on the end-user device (this is what end-to-end encryption like PGP or S/MIME does). So, if a device or server is compromised, emails stored there might still be readable.

Now it is important to note that TLS encryption in SMTP is opportunistic by default, meaning if one server doesn’t support TLS, the connection might proceed unencrypted to ensure mail delivery (making it backward compatible). MTA-STS (Mail Transfer Agent Strict Transport Security) is an excellent mechanism to enforce TLS encryption. It allows domains to publish policies stating that receiving mail servers must support TLS and have a valid certificate. It ensures emails are not delivered over insecure connections if an encrypted connection cannot be established between two communicating SMTP servers. This helps you make sure your business emails (which often contain sensitive company information) are encrypted in transit and cannot be intercepted by man-in-the-middle attackers.

Email Encryption Vs Email Authentication

Email encryption and email authentication are two different but complementary ways to ensure that the emails you send and receive are secure. Email encryption focuses on confidentiality – protecting the content of the message from being read by unauthorized parties. Email authentication focuses on verifying the sender’s identity – ensuring that the message genuinely came from the claimed source and hasn’t been forged by an attacker. Unencrypted messages can be intercepted and modified in transit without tipping off senders or recipients, potentially damaging relationships and causing disputes; encryption helps prevent this. Similarly, hackers can impersonate legitimate senders (spoofing), straining relationships and causing distress; authentication helps prevent this.

Definitions

Email Encryption: The process of encoding email message content and/or the connection it travels over into a format that is not readable by anyone except those who possess the correct key or are authorized recipients. Services employing S/MIME or PGP are often called end-to-end encryption services because they encrypt the message itself, protecting it from sender to receiver. TLS provides encryption for the communication channel (in transit).

Email Authentication: The process of verifying a sender’s identity using protocols like SPF, DKIM, and DMARC. These mechanisms check if the sending server is authorized for the domain (SPF), if the message content has been tampered with and signed by the domain owner (DKIM), and define actions for emails failing these checks (DMARC). Once verified, it provides assurance that the email is legitimate and can be used as evidence against fraud or phishing attempts.

The key difference is that email encryption protects the *content* from eavesdropping, while email authentication protects against *sender forgery* and phishing. It’s important to note that these technologies are not mutually exclusive—they should be used together as part of a comprehensive email security strategy. For example, encrypting an email ensures privacy, while authenticating it ensures it truly came from the expected sender.

To enable robust email authentication at your organization, implementing DMARC is crucial. Using a DMARC analyzer can simplify this process. It will help you automate your implementation, monitor results, prevent manual errors, and provide an added layer of security against spoofing and phishing, complementing your existing email encryption measures.

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About
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Ahona Rudra

Domain & Email Security Expert at PowerDMARC

Ahona is the Marketing Manager at PowerDMARC, with 5+ years of experience in writing about cybersecurity topics, specializing in domain and email security. Ahona holds a post-graduation degree in Journalism and Communications, solidifying her career in the security sector since 2019.

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