11 Guidelines for Businesses on Sending Secure Customer Emails

When customer data leaves your firm by email, the control question is who can open it, on what network, and with what evidence if something goes wrong.

Here are 11 steps to follow to send secure customer emails and protect sensitive information from unauthorised or unintended access.

Contents

• 1. Deploy an Email Policy
• 2. Don’t Use Public Wi-Fi
• 3. Know Your Compliance
• 4. Avoid Personal Devices
• 5. Use a Strong Password
• 6. Prioritise Staff Wellbeing
• 7. Apply Authentication
• 8. Invest in Encryption
• 9. Consider Email Revoke
• 10. Log Out of Accounts
• 11. Train Employees

1. Deploy an Email Policy

Deploying an email policy helps align employees with company aims and safety protocols.

The policy should outline essential responsibilities and regulations, helping staff maintain appropriate conduct and prioritise cybersecurity.

2. Don’t Use Public Wi-Fi

Public Wi-Fi is open to everyone, offering convenience but also a prime opportunity for cybercriminals.

Some networks may be fake hotspots designed to intercept data. Others may be vulnerable to man-in-the-middle attacks.

Always send customer data via a secured network.

3. Know Your Compliance

No matter your industry, you must uphold regulations. GDPR is one such requirement, ensuring businesses protect customer data.

Customer emails are a key focus. Staying on top of legislation ensures your communications remain compliant.

If you work in financial services, check out our email compliance checklist or explore the best secure email services for built-in compliance.

"Customer email security is not only an IT control. It is how firms show clients that sensitive data is handled with the same care in delivery as in storage."

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

Those expectations apply whether your team sends statements, onboarding packs, or one-off requests for sensitive documents.

4. Avoid Personal Devices

Remote working has popularised bring your own device (BYOD) practices.

These devices often lack adequate protection, making them targets for malware and other threats.

Use company-issued equipment or install protection software as standard.

5. Use a Strong Password

‘123456’ is still the most common password - and it takes less than a second to crack.

A weak email password gives cybercriminals easy access to all your customer conversations.

The National Cyber Security Centre recommends using a mix of uppercase and lowercase letters, numbers, and special characters. A great technique is combining three random words for strength and memorability.

6. Prioritise Staff Wellbeing

Burnout causes fatigue and stress, leading to mistakes - like sending sensitive info to the wrong recipient.

Ensure teams receive appropriate support and a healthy work-life balance. Read more in our 'Fighting Fatigue' whitepaper.

7. Apply Authentication

Two-factor authentication (2FA) is an essential safeguard. It requires identity verification before email content can be accessed.

Whether via SMS, Q&A, or another method, authentication adds assurance and helps avoid data breaches.

8. Invest in Encryption

Email encryption scrambles your messages and attachments to hide them from unauthorised third parties.

The Information Commissioner's Office (ICO) advises using encrypted channels when transmitting personal data.

Basic built-in encryption may not suffice in regulated sectors. Purpose-built secure email software provides encryption and authentication in one solution.

"Policy and training reduce risk, but misdirected messages and weak access controls still need encryption and recipient checks before personal data leaves the firm."

Michael Wakefield, CTO, Beyond Encryption (Mailock)

When a message has already left the firm, recall and revoke controls become the next line of defence.

9. Consider Email Revoke

Email recall allows you to take back an email sent in error - useful when sensitive data is involved.

Outlook's recall feature is limited. For reliable revoke capabilities, consider using dedicated email security software.

10. Log Out of Accounts

Threats aren’t always digital. Leaving your device unlocked or unattended risks unauthorised access.

Always log out of accounts and lock your screen before stepping away.

11. Train Employees

Even strong controls fail when teams are unsure what to do at send time.

Regular training keeps secure email habits specific to your workflows, not generic cyber awareness slides.

Run regular sessions so your team understands the risks and how to stay safe.

Get Protected

Following these steps will strengthen your customer email security. Security still needs ongoing review, and your team should know when controls change.

FAQs

What Do Secure Customer Email Guidelines Usually Cover?

They cover what information is being sent, who should receive it, how access is controlled, and what records are needed after the message is delivered.

Why Is Recipient Experience Part of Secure Email?

Customers are more likely to use a secure process when opening, reading, and replying feels clear. Security controls should protect sensitive information without creating unnecessary confusion.

Where Can Mailock Support Customer Email Workflows?

Mailock can support protected access, recipient authentication, secure replies, message tracking, and audit trails for customer emails that contain sensitive information.

References

GDPR Guidance and Resources, Information Commissioner's Office, 2024

Encryption Scenarios, Information Commissioner's Office, 2024

BYOD Statistics, Finances Online, 2023

Most Common Passwords List, NordPass, 2024

Three Random Words, National Cyber Security Centre, 2023

Reviewed by

Sam Kendall, 31.05.26

Sabrina McClune, 16.06.25

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