Should You Use Outlook to Send Confidential Data?

Email is a quick and simple way to exchange documents containing confidential information.

But should you send confidential data using a basic email provider like Microsoft Outlook?

The short answer is no - not with the default settings, and not without additional protection for sensitive data.

You should never send private information in an unprotected email using Outlook or any other email provider.

Messages are left open to risk at several points in their journey.

You should assume that anyone can intercept or manipulate them.

The good news is that there are a number of steps you can take to make your confidential data in Outlook more secure.

This article walks through encryption, account controls, and sending habits that help you send confidential data in Outlook without putting it at risk.

"Encryption is essential in protecting sensitive data, but it's just one piece of the puzzle.

A layered approach to security ensures better protection against modern cyber threats."

Mike Wakefield, CTO, Beyond Encryption (Mailock)

1. Use Encryption

The most important step you can take to protect confidential email data is to encrypt it.

Encryption scrambles the data so that it cannot be read by anyone who does not have the key.

However, it's important to note that not all encryption types offer the same level of security.

Encrypting an Email in Outlook

TLS (Transport Layer Security) encryption is used for all Outlook emails but is not considered secure enough alone for sensitive messages.

You can use additional encryption types to send a secure email in Outlook.

These are designed to increase the security barrier around your data:

S/MIME Encryption

Available to all Outlook users, you can set up an S/MIME certificate to encrypt an email in Outlook.

S/MIME provides relatively strong protection against interception but can only be used with systems that have certificates.

For this reason, usage of S/MIME is quite limited.

Microsoft Purview Message Encryption

Available with eligible Microsoft 365 and Office 365 plans, Microsoft Purview Message Encryption is more user-friendly than S/MIME for many organisations and supports encrypted messages with rights management controls.

However, availability and recipient experience depend on licence, tenant settings, policy configuration, and the recipient's mail client.

Microsoft also treats revocation as conditional: Advanced Message Encryption can revoke eligible link-based, branded encrypted emails, but not messages delivered through the native inline experience in supported Outlook clients.

For customer communications, firms should check whether the experience, verification method, and administration model fit their volume and support needs.

Learn how to encrypt an email in Outlook.

Or, read our review of Microsoft's secure email.

Third-Party Secure Email Solutions

Third-party secure email solutions are designed to add controls around built-in encryption options, offering features that can enhance security and usability for specific customer workflows.

These solutions often include recipient authentication, helping firms check access before sensitive content is opened, and audit trails for tracking access.

Many also provide advanced encryption for complete end-to-end protection (from outbox to inbox).

Depending on the organisation, third-party solutions may be easier to deploy and manage for day-to-day customer communication than configuring Microsoft-native policies alone.

For instance, Mailock integrates with supported Outlook environments and adds secure sending, recipient authentication, secure replies, revoke, tracking, and audit trail capabilities.

Choosing the right secure email solution depends on your specific needs, but third-party options often provide the flexibility and security required for protecting sensitive customer communications.

Read our review of the best secure email services.

Summary: Is Outlook's Encryption Secure?

Microsoft's own guidance shows that its encrypted email capabilities depend on licence, tenant configuration, policy setup, recipient experience, and whether advanced controls such as link-based revocation are available for the message.

Businesses sending highly sensitive or personal customer data are required by the ICO (Information Commissioner's Office) to secure it.

A secure email solution can add advanced encryption, recipient authentication, and audit capabilities for stronger control over sensitive customer messages.

Many of these solutions offer Outlook encryption add-ins that bring security features to your email client's navigation menu.

2. Use Strong Passwords

When setting up your email account (or your encryption), it is important to use strong passwords.

"A strong password is your first line of defence.

Using a password manager makes your credentials unique and secure."

Adam Byford, CCO, Beyond Encryption (Mailock)

Strong passwords are at least 12 characters long and include a mix of upper and lowercase letters, numbers, and symbols.

In addition to creating strong passwords, it's crucial to avoid reusing passwords across different accounts.

Using unique passwords can significantly reduce the risk of security breaches, especially if one of your accounts is compromised.

If you are sending confidential business data, it is vital these practices are in place for individual and administrator accounts.

3. Check Email Addresses

Only send confidential data to people you trust.

Before sending the message, take a moment to check the recipient's email address.

You can do this by hovering over the email address to see if it is a valid address in the correct structure with the correct spelling.

No matter how careful you are, you could still email the wrong person.

It's one of the top causes of a data breach.

That's why many businesses use recipient authentication to make sure highly confidential emails can only be accessed by the right people.

4. Recall Misfired Emails

If you send information to the wrong person, you need a way to retract it.

Outlook offers some recall features that allow you to retrieve messages sent in error. However, there are a few limitations:

• Both sender and recipient usually need Microsoft 365 work or school accounts in the same organisation.
• The email must be unopened.
• A recipient's spam filters can interrupt the process.

If you're sending highly sensitive information, you can't rely on these limited native email recall features.

To improve post-send control for sensitive emails, you may need a more advanced solution.

Tools like the Mailock Outlook add-in, or other secure email platforms, can offer stronger options for email revocation and security where their controls fit your workflow.

Exploring multiple secure email tools can help determine the best fit for your needs.

5. Enable Account 2FA

Turning on two-factor authentication for your Outlook account means you can only sign in with your password after verifying access to a secondary device, such as your smartphone.

This security measure significantly reduces the chance of an inbox takeover.

It protects against 99.9% of automated attacks, according to Microsoft.

It's a simple but effective measure to make sure you are the only person with access to confidential data in your account.

Again, if you're handling sensitive data, two-factor authentication should be enabled for all accounts, especially administrators.

6. Know the Risks

No matter how careful you are, there will be risks that data could be leaked or intercepted, and there are always new risks arising.

If you regularly send confidential data using Outlook, it's important to be aware of the risks so you can be vigilant.

For businesses, employees must be regularly trained to keep them up-to-date with new threats.

Additional risks to be aware of include:

Phishing Scams

Phishing scams are emails designed to trick you into giving away your personal information.

Don't click on links or open attachments from emails that you don't trust or from people you don't trust.

Malware

Malware is software that can be used to steal your data, monitor your activity, or damage your computer.

Be careful about the sites you visit and the files you download from incoming emails.

Inbox Attacks

Inbox takeover attacks happen when hackers unlawfully breach your email account, gaining access to your private communications.

You should always protect sensitive emails with authentication, creating an additional barrier in case an inbox is compromised.

A Note on the Importance of Data Classification

Data classification is the process of sorting information by its sensitivity and value.

For example, customer credit card details are more sensitive than a company newsletter.

By understanding the level of sensitivity, you can decide on the right security measures.

Highly sensitive data might need encryption, access restrictions, or digital rights management (DRM) tools.

Classifying your data helps you focus your security on protecting the most valuable information.

Sending Confidential Data?

Use encryption, strong passwords, and if you're a business sending highly confidential data, use a secure email solution.

Examples include Mailock, Zivver, and Egress, but evaluating multiple options can help you select the one that best fits your needs.

You won't ever protect against every eventuality, but you can make it very difficult for anyone to compromise your data.

Follow the steps in this post and you'll vastly enhance the security of your confidential data when using Outlook.

FAQs

Is Outlook’s Default Encryption Enough for Sensitive Data?

Outlook’s built-in encryption (TLS) is not advanced enough to safeguard highly confidential information.

You should add more advanced encryption or use a secure email solution for better protection.

How Do I Retract an Email Sent to the Wrong Person?

Outlook includes recall features, but they work under limited conditions and often fail.

For stronger post-send control, you’ll need a secure email solution with a dedicated revoke function.

Should I Enable Two-Factor Authentication?

Yes - two-factor authentication adds a crucial extra layer of security, significantly reducing the risk of unauthorised account access.

Do Third-Party Secure Email Solutions Offer Better Protection?

They often provide features like recipient authentication, advanced encryption, and better scalability.

But they may require extra investment and administrative oversight.

How Do I Choose the Right Secure Email Platform?

Assess your security needs, regulatory obligations, and user requirements.

References

Microsoft 365 Secure Email vs Mailock: A Comparison, Beyond Encryption, 2024

Message Encryption FAQ, Microsoft Learn, 2026

Revoke Email Encrypted by Advanced Message Encryption, Microsoft Learn, 2026

How to Recall an Email in Outlook: Requirements, Limitations & Steps, Microsoft Support, 2026

Security Requirements, Information Commissioner's Office, 2024

Data Security: An Analysis of the Latest ICO Findings, Beyond Encryption, 2023

One Simple Action You Can Take to Prevent 99.9 Percent of Account Attacks, Microsoft, 2019

Reviewed by

Sam Kendall, 02.06.26

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