Types of Email Encryption

Have you ever wondered how secure your emails really are?

Cybercriminals are getting more advanced every year, making email encryption increasingly important for protecting email information.

As someone who's helped companies to protect their communications for years, I’ve seen the devastating impact a lack of proper security can have.

From data breaches to financial losses, the consequences can be serious.

Fortunately, understanding the different types of encryption can empower you to safeguard your communications.

In this guide, I’ll walk you through the most effective encryption methods, from widely adopted standards like TLS to the highly secure AES-256.

Along the way, I’ll share practical insights from working in the field, helping you to make the best decisions about protecting your emails from threats.

Contents:

• Why Email Encryption Matters
• Main Types of Email Encryption
• Additional Types of Encryption
• Understanding Email Encryption

Why Email Encryption Matters

Email encryption is crucial for keeping sensitive information private and secure.

With cyber threats constantly evolving, simply sending a 'normal' email is no longer safe.

It could be intercepted or manipulated at many points in its journey.

By using the right types of encryption, you can make sure that even if your email is intercepted, the contents are unreadable to anyone without the right decryption key.

Unfortunately, not all types of email encryption are alike.

For example, TLS (Transport Layer Security) is used by a lot of email providers to secure data in transit, but it only encrypts content between email servers, leaving messages unprotected in inboxes.

To protect data from sender to receiver (called end-to-end email encryption), it's important to know the difference between the different types.

Types of Encryption for Email Security

Email encryption can be split into two main categories: transport-level encryption and end-to-end encryption.

Each type serves a specific purpose in protecting your emails, and understanding these differences is key to choosing the right security.

1. Transport-Level Encryption: SSL and TLS

SSL (Secure Sockets Layer)

SSL was introduced in 1995 as one of the first protocols to secure email content through authentication and encryption.

Cyber experts don't recommend using SSL for email because it’s prone to attacks. TLS, which builds on SSL’s foundation, is the modern standard.

TLS (Transport Layer Security)

TLS was developed in 1999 as an upgrade to SSL, and addresses a lot of its security flaws.

TLS encrypts emails while they are in transit, protecting the data as it flows between web applications and servers.

By encrypting email content as it travels across networks, TLS ensures that data remains private until it reaches its destination.

A common implementation of TLS is STARTTLS, which upgrades unsecured connections to encrypted ones, blocking interception by eavesdroppers.

"While TLS is essential for securing data in transit, it’s important to recognise its limitations. Organisations should think about layering different types of encryption to cover all vulnerabilities."

— Mike Wakefield, CTO, Beyond Encryption

As noted above though, TLS doesn't provide end-to-end encryption.

If emails are stored unencrypted on servers (for example, when they are in people's 'Sent' or 'Inbox' folders), they can be vulnerable to attack.

2. End-to-End Encryption: PGP and S/MIME

PGP (Pretty Good Privacy)

Developed in 1991, PGP was a game-changer in encryption (hence the 'pretty good').

It's what's known as asymmetric encryption, and it involves a public key to encrypt emails and a private key to decrypt them.

Technically, PGP secures email content by combining both symmetric and asymmetric techniques — but the essential takeaway is that it creates a situation where only the intended recipient can decrypt the message.

S/MIME (Secure/Multipurpose Internet Mail Extensions)

S/MIME is an encryption standard that adds digital signatures to emails to verify they are authentic.

Developed by RSA Data Security, S/MIME is built into most major email platforms, making it easy to use in corporate settings.

S/MIME encrypts emails using public-key cryptography and verifies the sender’s identity through digital signatures.

However, users first need to obtain digital certificates from a trusted Certificate Authority (CA).

"S/MIME is ok for enterprise use because it integrates with most corporate systems. But there’s a trade-off: the cost and complexity of managing digital certificates can be high."

— Paul Holland, CEO and Founder, Beyond Encryption

3. AES-256: The Gold Standard for Symmetric Encryption

AES-256 (Advanced Encryption Standard - 256-bit) is one of the most secure types of encryption available.

Trusted worldwide, it is used to protect everything from government communications to financial information.

AES-256 uses a 256-bit key to encrypt data, making it virtually immune to brute-force attacks (it would take many, many years to crack).

Only authorised parties with the correct decryption key can access the encrypted content.

• Advantages of AES-256 email encryption:
  • Nearly unbreakable encryption, even with the most powerful computers.
  • Encrypts and decrypts data quickly, making it ideal for secure communications.
  • Works across different platforms without requiring complex key management, simplifying deployment.

"AES-256 underpins many of our secure communication platforms at Beyond Encryption. It strikes the perfect balance between speed and security, making it essential for industries that handle sensitive data daily."

— Adam Byford, Chief Commercial Officer, Beyond Encryption

Additional Types of Encryption

Encrypted PDFs and Attachments

Sending sensitive information as encrypted attachments, such as PDFs or ZIP files, adds an extra layer of security.

This ensures that even if the email content is intercepted, the attachments remain inaccessible without the correct decryption key.

This is not the same as a password-protected document in Microsoft Word — which can quite easily be cracked by hackers.

There are various methods of encrypting files and they can use any number of encryption algorithms, some of which are more or less secure.

Web/Client Portal Encryption

Email content is sometimes encrypted and sent to a secure web portal, where it can be accessed by clients or customers.

The drawback of this approach is that people need an account and must log in to view messages, but it reduces the risk by a substantial amount.

This approach is particularly favoured by organisations that need to comply with strict data protection regulations, such as financial services firms or legal practices.

While it can be useful for customers to have an online store of all their communications from an organisation, it is also recommended to deliver content by secure email so that clients don't have to log in every time they receive information from you.

"Customer portals are ideal for regulated industries, where you need that auditable store of communications as a customer and as a business. But without the ability to email securely, in real-time, you lose that immediacy factor."

— Carole Howard, Head of Network Sales, Beyond Encryption

Understanding Email Encryption

Understanding the different types of encryption is crucial for protecting email communications.

While TLS is a great starting point for securing data in transit, end-to-end encryption methods like PGP and S/MIME offer greater security for sensitive information.

AES-256 remains the gold standard, providing a robust, efficient solution for industries where data security is paramount.

A layered strategy, combining encryption with other security practices, such as strong authentication and ongoing user training, is your best defence against cyber threats.

You can keep your communications safe by staying informed and proactive in relation to digital risks.

FAQs

What Are the Most Common Methods of Email Encryption?

The two main types of email encryption are transport-level encryption and end-to-end encryption. Transport-level encryption, like TLS, secures data while it's in transit between servers. End-to-end encryption methods, such as PGP and S/MIME, ensure that only the intended recipient can decrypt and read the content.

Is Outlook Email Encrypted?

Outlook does offer email encryption, but the level of security depends on how it's configured. By default, emails sent through Outlook use TLS to secure data in transit. However, for complete end-to-end encryption, you may need to set up additional features like S/MIME or use third-party encryption services.

What Is the Easiest Way to Encrypt an Email?

The easiest way to encrypt an email is to use a service that automatically applies encryption, such as a secure email provider that offers built-in options. For more advanced security, using S/MIME or PGP can be beneficial, though these require additional setup and key management.

How Can I Tell if an Email Is Encrypted?

You can check if an email is encrypted by looking for a lock icon in your email client, which indicates that TLS is being used. For end-to-end encrypted emails, you may need to check the security settings or use specific software to verify the encryption keys.

What Type of Encryption Does Outlook Use?

Outlook primarily uses TLS to encrypt emails in transit, making sure the data is secure between email servers. For more advanced security, Outlook can use S/MIME to provide end-to-end encryption, but this requires obtaining a digital certificate from a trusted authority.

What Is the Difference Between AES and RSA?

AES is a symmetric encryption algorithm, meaning it uses the same key for both encryption and decryption. It’s known for being fast and secure. RSA, on the other hand, is an asymmetric encryption algorithm that uses a pair of keys — a public key for encryption and a private key for decryption. AES is typically used for securing large amounts of data efficiently, while RSA is often used for secure key exchange when immediacy isn't required.

Are All Emails Sent Encrypted?

No, not all emails are encrypted. While many email providers use TLS to secure data in transit, emails stored in your inbox may not be encrypted. End-to-end encryption is not standard and requires additional configuration, meaning emails can still be vulnerable if this isn’t set up.

How Do You Send Files Securely Over Email?

To send files securely over email, consider encrypting them separately, for example, using AES-encrypted ZIP files or encrypted PDFs. Alternatively, you can use a secure client portal or a dedicated file-sharing service with built-in encryption. Always avoid using simple password protection as it can be easily bypassed.

References:

Secure E-mail Communications Through Cryptographic Techniques—A Study, Springer, 2020

What is Email Interception?, Beyond Encryption, 2024

Usability of End-to-End Encryption in E-Mail Communication, Frontiers in Big Data, 2021

Advanced Encryption Standard (AES), NIST, 2001

Email Security Issues, Tools, and Techniques Used in Investigation, MDPI, 2023

Managing Access to Confidential Documents: A Case Study of an Email Encryption Solution, MDPI, 2023

Reviewed by:

Sabrina McClune, 28.11.24

Sam Kendall, 15.11.24