Secure Email for Financial Services: A Complete Guide

Email remains the primary channel through which advisers, platforms, and providers communicate with clients - yet it is also the channel most exposed to human error, interception, and compliance risk.

With the FCA shifting durable-medium expectations towards digital-by-default, and with increasing scrutiny under Consumer Duty, financial organisations need secure email processes that protect client data and deliver reliable evidence of delivery and access.

This guide brings together research, regulation, and practical implementation advice to help regulated firms choose, configure, and operate secure email in a compliant, user-friendly way.

Contents

• Why Secure Email Matters in Financial Services
• What Secure Email Is - and What It Isn’t
• Common Email Risks: Interception, Phishing, Human Error
• Email Compliance Expectations (GDPR, FCA, MiFID)
• The FCA’s Digital-By-Default Durable-Medium Shift
• Secure Email Gateways: Inbound vs Outbound
• Comparing Secure Email Providers for Financial Services
• What Counts as PII - and When to Encrypt It
• Best Practice for Advisers and Providers
• How to Choose a Secure Email Solution

Why Secure Email Matters in Financial Services

Financial services professionals handle some of the most sensitive categories of personal data: financial history, investment behaviour, medical details for protection products, identity documents, and regulatory disclosures.

Email is still the channel most often used to send this information - yet it was never designed to be secure.

And at global scale, volume alone increases exposure - with email volumes reaching into the hundreds of billions per day.

The Risk Landscape Is Expanding

Cyber threats continue to evolve.

Phishing and social engineering remain among the most common routes into organisations, and the wider cost of breaches continues to rise in breach reporting.

Interception also remains a credible risk wherever data travels without encryption.

But the most frequent problem is still everyday human error - a mis-typed email address, the wrong file attached, or a message forwarded to a personal mailbox.

In our research on UK consumers, one in four people reported sending personal data to the wrong recipient.

"Most regulated organisations don’t struggle with a lack of policy. They struggle with day-to-day misdelivery risk - the human moments where the wrong email address or attachment becomes a reportable incident."

Carole Howard, Head of Networks, Beyond Encryption

What Secure Email Is - and What It Isn’t

Adding Protection to a Vulnerable Channel

A secure email service adds layers of security to email infrastructure you already use.

These layers typically include:

• Encryption - protecting content at rest and in transit
• Recipient authentication - making sure only the intended person can open it
• Audit trails - recording access for compliance
• Revoke - removing access to mis-sent messages
• Security alerts - prompting secure send when sensitive content is detected

Many of these protections support compliance expectations under GDPR and relevant FCA and MiFID requirements, particularly where organisations follow ICO guidance on applying encryption as a safeguard.

For more information on choosing a secure email solution, see our dedicated guide: The Best Secure Email Services for Business.

Common Email Risks

Interception

Email interception occurs when a third party gains access to a message in transit or on a mail server.

Without encryption, intercepted content can be read in plain text, exposing personal and financial information.

Phishing

Phishing remains one of the most reported cyber attack methods worldwide.

It involves deceptive emails or messages that appear to come from trusted organisations, tricking recipients into clicking malicious links or sharing confidential information.

Attackers impersonate banks, insurers, and pension providers to harvest logins or payment details.

Human Error

The ICO consistently reports misdelivery as one of the top causes of reportable data breaches in the UK, with enforcement activity regularly referencing the consequences of sending personal data to the wrong recipient.

Errors are predictable - which is why secure email systems must:

• Warn users about sensitive content
• Require authentication for risky messages
• Enable revoke if something goes wrong

Email Compliance Expectations (GDPR, FCA, MiFID)

Email touches multiple regulatory frameworks, including:

GDPR: Protecting Personal Data

GDPR requires organisations to implement “appropriate technical and organisational measures” to protect personal data.

Encryption is explicitly recognised as an appropriate safeguard in ICO guidance.

FCA COBS & SYSC: Record Keeping

Firms must keep records of communications - including electronic - in a durable medium.

They must be retrievable, tamper-resistant, and accessible to the regulator.

The FCA’s own durable medium definition is a useful reference point for what this means in practice.

MiFID II & ESMA Guidance

MiFID organisational requirements place expectations on firms to secure communications, authenticate information transfers, and prevent unauthorised access.

Together, these obligations create a practical principle:

If an email contains personal data, financial data, or a regulated disclosure, encryption and access controls are often appropriate - and should be applied based on risk.

For more details see: Email Compliance Checklist for Financial Services.

The FCA’s Digital-By-Default Durable-Medium Shift

What’s Changing?

From 12 January 2026, the FCA will treat electronic communication as the default durable medium for MiFID-derived retail disclosures.

This change, outlined in PS25/13 and summarised in our guide to the durable-medium reform, confirms that electronic delivery is expected where it meets durable-medium criteria.

A durable medium must enable clients to:

• Receive information personally addressed to them
• Store it for future reference
• Reproduce it unchanged

Encrypted delivery can support these conditions, provided the chosen approach includes appropriate controls such as:

• Encryption suited to the risk
• Identity verification or equivalent access controls
• Reliable audit records

Secure Email Gateways: Inbound vs Outbound

Secure email gateways (SEGs) protect email traffic at scale.

Inbound Gateways

Inbound SEGs block threats before they reach users.

• Phishing and spoof detection
• Malware and attachment scanning
• Spam filtering
• AI-driven behaviour analysis

Outbound Gateways

Outbound SEGs secure information leaving the organisation.

• Automatic encryption
• Recipient authentication
• DLP (Data Loss Prevention)
• Message revoke
• Audit trails

For a full breakdown, see our guide: What Is a Secure Email Gateway?

Comparing Secure Email Providers for Financial Services

We analysed major business email providers and secure email services in our comparative guides:

• Best Email Providers for Financial Services
• Best Secure Email Services for Business

Here is a condensed overview of the options for financial services secure emailing:

Summary Comparison

• Mailock - AES-256 encryption, recipient authentication, secure replies, revoke, tracking, Outlook integration. Purpose-built for regulated sectors.
• Microsoft 365 (Purview OME) - Strong encryption but limited recipient verification. Requires advanced configuration.
• Gmail (Workspace CSE) - Enterprise-grade encryption but no native identity checks.
• Egress - Outbound-focused with machine-learning prompts and authentication.
• Zivver - Large file transfer and AI prompts, SMS codes.
• Mimecast / Proofpoint - Enterprise-scale gateways with robust inbound controls.

For firms handling sensitive documents daily, verification combined with encryption is often the decisive factor - especially where firms need stronger assurance than email-address-only access provides.

What Counts as PII - and When to Encrypt It

Our full guide, What Counts as PII and Why?, breaks down the categories of information that require protection.

The Puzzle Model of Identity

PII includes:

• Direct identifiers - name, address, ID numbers
• Indirect identifiers - DOB, job title, postcode
• Special category data - health, ethnicity, biometric data

A single data point may be low-risk.

Combined data points can reveal a great deal.

The rule of thumb: If you wouldn’t write it on a postcard, encrypt it.

Best Practice for Advisers and Providers

1. Use a Secure Channel for High-Risk Personal Data

Anything containing customer data should be protected in a way that matches the risk.

For many regulated use cases, that means encryption plus access control, aligned with ICO guidance.

2. Authenticate Recipients

Email-address-based security is not always enough for regulated documents.

Where the content is sensitive, a second factor (SMS or a question and answer) provides stronger assurance.

3. Revoke Mis-Sent Emails

Revoke should function as a safeguard after a message has been sent.

Where possible, it should also work after a message has been opened.

4. Maintain Audit Trails

Record what was sent, when, and who accessed it.

This supports oversight, incident response, and regulatory evidence needs.

5. Integrate with Archiving

Durable-medium content must be retained in a tamper-resistant format, and remain accessible for the required retention period.

How to Choose a Secure Email Solution

Checklist

• Does it support end-to-end AES-256 encryption?
• Does it offer recipient authentication beyond email address?
• Can clients reply securely for free?
• Does it include revoke after opening?
• Does it maintain detailed audit logs?
• Does it integrate into workflows (e.g., Outlook add-in, API, gateway)?
• Is it aligned with relevant GDPR, FCA, and MiFID expectations?

Mailock secure email is designed around these needs and is already in use across the UK’s financial services sector.

FAQs

Does Secure Email Replace Client Portals?

No. Portals still support storage and self-service journeys. Secure email complements them for high-importance, time-sensitive documents.

Do Clients Need to Opt In?

Under durable-medium reforms, electronic communication can be the default, as long as clients can still request paper.

Is It Overkill to Encrypt Everyday Emails?

No. Many breaches start with routine communication errors rather than exceptional events.

Can Secure Email Prevent Human Error?

It cannot eliminate error, but authentication, revoke, and security alerts can significantly reduce its impact.

References

ICO GDPR Security Guidance, 2024

FCA Policy Statement PS25/13, 2025

FCA Durable Medium Glossary Definition, 2025

Statista Email Volume Data, 2023

IBM Cost of a Data Breach Report, 2023

Reviewed by

Sam Kendall, 22.01.26