Every day, millions of business emails carry sensitive data — from contracts and invoices to patient records and financial details. Shockingly, over 90% of cyberattacks begin with email phishing or breaches. If your Outlook emails aren’t encrypted, confidential information could easily fall into the wrong hands.

The good news? Microsoft Outlook offers built-in encryption features to help secure communications. In this guide, we’ll break down how to send an encrypted email on Outlook, why it matters, and what best practices you should follow.

Why Encrypt Emails in Outlook?

The Growing Threat of Email Breaches

Emails are prime targets for hackers. In recent years, organizations have suffered multimillion-dollar losses due to business email compromise (BEC) and phishing attacks. Attackers intercept unencrypted emails to steal passwords, financial data, or proprietary information.

By encrypting messages in Outlook, you ensure that only the intended recipient can read the contents. Even if an attacker intercepts the email, it remains unreadable without the decryption key.

Compliance & Legal Requirements

Encryption isn’t just about protection — it’s often a legal obligation. For example:

  • Healthcare organizations must follow HIPAA rules.

  • Financial services face SOX and PCI DSS compliance.

  • Global enterprises must meet GDPR encryption requirements.

Failing to encrypt sensitive Outlook emails could expose your business to penalties, lawsuits, and reputational damage.

Methods of Sending Encrypted Emails in Outlook

Microsoft Outlook provides multiple ways to encrypt emails, depending on your setup and subscription.

Office 365 Message Encryption (OME)

If you have a Microsoft 365 subscription, you can use OME. This allows you to:

  • Send Encrypt-Only messages, where recipients can read but not forward.

  • Use Do Not Forward, which prevents copying or printing.

  • Send to recipients outside your organization securely.

S/MIME (Secure/Multipurpose Internet Mail Extensions)

S/MIME is a certificate-based encryption method. Both the sender and recipient need digital certificates. While setup is more complex, S/MIME is widely used in enterprise environments that require strong, end-to-end encryption.

Third-Party Encryption Tools

Some businesses add an extra layer of encryption through third-party tools. These may include secure email gateways or DLP (Data Loss Prevention) integrations that automatically enforce encryption policies.

Step-by-Step Guide – How to Send an Encrypted Email on Outlook

Now, let’s walk through the exact process for encrypting emails in different versions of Outlook.

For Office 365 Users (Windows & Mac)

  1. Open Outlook and create a New Email.

  2. Go to the Options tab.

  3. Select Encrypt.

  4. Choose between Encrypt-Only or Do Not Forward.

  5. Click Send.

Recipients will receive instructions on how to view the encrypted message.

For S/MIME Users

  1. Install a digital certificate from a trusted provider.

  2. In Outlook, go to File → Options → Trust Center → Trust Center Settings → Email Security.

  3. Import and configure your certificate.

  4. When composing a new message, go to Options → Permissions → Encrypt with S/MIME.

  5. Send securely.

For Outlook Web/Outlook.com

  1. Log in to Outlook on the web.

  2. Select New Message.

  3. At the top menu, click Encrypt.

  4. Choose Encrypt-Only or Do Not Forward.

  5. Send the message.

Best Practices for Secure Email Communication

Encryption is powerful, but it works best when combined with other security measures:

  • Verify recipients carefully: Double-check email addresses to avoid accidental leaks.

  • Enable MFA (Multi-Factor Authentication): Protect your Outlook account itself.

  • Avoid sensitive data in subject lines: Subjects are often not encrypted.

  • Educate employees: Train teams to recognize phishing and social engineering attempts.

Common Issues & Troubleshooting Outlook Email Encryption

Even with the right setup, you may face issues. Here are common problems and fixes:

  • Recipient can’t open encrypted email: Ensure they have a Microsoft account or follow the secure link instructions.

  • Missing S/MIME certificate: Both parties must have valid certificates installed.

  • Compatibility issues: Some non-Outlook email clients may not support encryption. Use OME for broader compatibility.

FAQs – Sending Encrypted Emails in Outlook

Q1: Is Outlook email encryption free?
Yes, Office 365 Message Encryption is included in most Microsoft 365 plans. S/MIME requires a certificate, which may involve costs.

Q2: What’s the difference between OME and S/MIME?
OME is cloud-based and works with external recipients. S/MIME is certificate-based and ideal for enterprise-level security.

Q3: Can recipients without Outlook open encrypted emails?
Yes. They receive a secure link that allows them to view the message.

Q4: Do I need a digital certificate to encrypt emails?
Only for S/MIME. OME works without certificates.

Q5: How secure is Outlook’s email encryption compared to Gmail?
Both provide strong encryption, but Outlook’s OME offers more enterprise-grade controls.

Q6: Can businesses enforce encryption policies automatically?
Yes. Administrators can configure DLP and mail flow rules to enforce encryption.

Final Thoughts

Learning how to send an encrypted email on Outlook is essential for modern professionals and business leaders. With cyberattacks and compliance pressures growing, securing your communications isn’t optional — it’s a necessity.

Outlook makes it straightforward, whether you use OME, S/MIME, or third-party tools. By combining encryption with strong security practices, you protect not just data, but also trust, compliance, and reputation.

Start encrypting your Outlook emails today — because your next email could be the one attackers are waiting for.