The Best Secure Email Services to Protect Your Business Data

Email is one of the most widely used communication methods in business, but without robust protections, every message could be a target for cyber attack or data breach.

Thankfully, there's a wide range of secure email services available to help your organisation protect sensitive information and maintain privacy.

We've assessed the most widely used secure email providers based on their encryption methods, authentication options, usability, and pricing.

Comparison: We make Mailock, one of the products compared here, so we are not neutral. Details of other products come from their own published information and may have changed since this article was last reviewed. How we write comparisons.

What Is a Secure Email Service?

A secure email service adds multiple layers of protection to standard email, offering safeguards like encryption, identity authentication, audit trails, and message revoke features.

The goal is to reduce the risk of email-based threats such as interception, data loss, or misdelivery while helping businesses stay compliant.

Why Do You Need a Secure Email Service?

Email was never designed to be a secure channel. Yet today, it underpins most business communications.

With the rise in remote work and cloud platforms, threats remain widespread. 43% of UK businesses reported a cyber security breach or attack in the 12 months before the government's 2025/2026 survey. Phishing attacks were the most common type by far.

And it's not just malicious attacks. Misdirected emails remain a leading cause of breaches.

The majority of breaches involve a human element.

"Most firms do not need another inbox. They need outbound controls that fit how people already send email."

Adam Byford, COO, Beyond Encryption (Mailock)

Types of Secure Email Service

Different providers specialise in different threat vectors. Some offer protection from inbound threats, others focus on outbound security.

• Outbound email security protects sensitive data leaving your organisation, helping prevent unauthorised access.
• Inbound email security scans incoming messages for threats before they reach users.

Large organisations might opt for a secure email gateway to enforce policies at the server level.

Smaller firms may prefer desktop-based software to apply protections on an individual user basis.

Choosing a Secure Email Service

Look for these key features when evaluating your options:

• AES-256 encryption (Advanced Encryption Standard), widely trusted across industries.
• Recipient authentication - add assurance about who opens a message before protected content is shown.
• Message revoke - close future access if you send something in error.
• Audit trails - track message access and prove compliance.

At a Glance

The table below summarises the providers covered in this guide. Check each vendor's site for current limits, features, and pricing before you choose.

Use the summary above as a starting point, then read the fuller notes on each provider below.

Best Secure Email Services

There's no one-size-fits-all. From Microsoft Purview to Mailock, each service offers a different mix of protections and experiences.

Mailock Secure Email

Mailock is an outbound secure email service that works with your existing email setup.

It is available as a desktop app or an enterprise gateway.

Features include:

• AES-256 encryption, with unlimited secure replies for recipients.
• Recipient authentication via SMS, Q&A, or email verification, plus Unipass ID sign-in for financial services.
• Message revoke for sent messages and attachments.
• Notifications when protected content is accessed.
• Audit trails covering message access and revoke events.
• Security alerts that prompt secure sending based on message content.

Key considerations: Recipients can read and reply to Mailock emails without an account. A free account lets them send their own secure email. Includes an Outlook add-in for supported classic Outlook for Windows.

Microsoft Purview Message Encryption

Microsoft Purview Message Encryption is included with several Microsoft 365 and Office 365 plans, including Enterprise E3/E5, Microsoft 365 Business Premium, and some education and government plans. Availability still depends on licence, tenant configuration, and policy setup.

Features include:

• AES-256 encryption, with encrypted replies.
• Conditional revocation for eligible link-based encrypted messages when Advanced Message Encryption is configured.
• Inbox access verification via Microsoft or Google login, or one-time codes.
• Read receipts, configurable by sender and recipient.
• Audit dashboard showing timestamps, recipients, and access status.

Key considerations: Access verification is via Microsoft or Google login or one-time codes, rather than selectable recipient checks such as SMS or Q&A.

Read our full review of Microsoft's secure email.

Egress Cloud Email Security Suite

Egress, a KnowBe4 company since 2024, combines email protection tools into one suite, with Defend, Prevent, and Protect modules to guard against inbound and outbound threats.

Features include:

• AES-256 encryption, applied by users or admins.
• Access privileges such as restrictions on forwarding or downloading.
• Recipient authentication via an Egress account with SSO support, a pre-shared secret, or a one-time URL.
• Machine learning prompts for secure sending.
• Microsoft 365 integration with Outlook add-in.

Key considerations: Recipients usually sign in to a free Egress account to read and reply, unless the sender uses one-click access. Check Egress for current reply limits and credit allowances.

Compare Egress vs Mailock.

Zivver Secure Email

Zivver, now part of Kiteworks, helps reduce the risk of outbound errors, with machine learning tools and secure file transfers up to 5TB.

Features include:

• AES-256 encryption for messages and attachments.
• Access code, SMS, and email authentication.
• Secure file transfer (large file sizes).
• Email expiration and recall features.
• Contextual correction using AI prompts.

Key considerations: Zivver offers an Outlook add-in and Chrome extension. Some features vary by licence tier.

Read our Zivver vs Mailock guide.

Mimecast Secure Email Messaging

Mimecast is best suited to enterprises needing high-scale email security and continuity.

Features include:

• AES-256 encryption based on rules or manual triggers.
• Message expiration and recall options.
• Two-factor authentication for users.
• Read notifications for senders.
• Custom branding for outbound secure messages.

Key considerations: At the time of writing, Capterra lists Mimecast Email Security at 4.3/5 from 80 reviews. Mimecast does not publish standard pricing on its secure messaging page, so buyers should request a quote.

See how Mimecast compares to Mailock.

Proofpoint Email Encryption

Proofpoint is a compliance-focused provider with admin controls and policy-based encryption settings.

Features include:

• AES-256 encryption configured through content rules.
• Message revoke at admin level.
• Integration with Outlook and Gmail.

Key considerations: External recipients use Proofpoint Secure Mail, a web-based interface, to read and respond to encrypted emails.

Proofpoint's newer encryption experience lists a default 30-day encrypted thread access period, with options to enforce shorter access periods.

Explore our Proofpoint vs Mailock comparison.

The Best Secure Email?

Email isn't going anywhere - but the way we secure it must evolve.

Each provider offers a unique mix of protections.

"There is no single best secure email for every firm. The right choice depends on whether you need outbound protection on your existing inbox, enterprise gateway rules, or a full inbound and outbound suite."

Paul Holland, Founder and CEO, Beyond Encryption (Mailock)

Going by the summary table, Microsoft Purview Message Encryption suits Microsoft 365 enterprise estates, and Egress suits firms that want one inbound and outbound security suite. Mimecast is aimed at large-scale enterprise email security, Proofpoint at compliance-led policy encryption, Zivver at large file transfer and outbound error reduction, and Mailock at outbound protection on your existing inbox.

FAQs

What Should Businesses Compare in Secure Email Services?

Compare encryption, authentication, recipient experience, secure replies, integrations, admin controls, audit trails, and pricing fit.

Why Does Workflow Matter When Choosing a Provider?

A secure email service only works well if senders and recipients can use it consistently in real business communication.

How Should Firms Compare Recipient Access and Audit Evidence?

Check whether recipients need accounts, how identity is verified, whether replies stay protected, and what records are available after sending.

References

Cyber security breaches survey 2025/2026, Department for Science, Innovation and Technology, 2026

Secure Email, Zivver, 2026

Recipient Verification Methods, Zivver, 2026

Protect Your Organization With Secure Messaging, Mimecast, 2026

New Email Encryption Experience, Proofpoint, 2024

2026 Data Breach Investigations Report, Verizon, 2026

Reviewed by

Sam Kendall, 16.10.26

Sabrina McClune, 07.06.24

Read our editorial policy.

This content is for general information only and is not legal advice.