How to Send Secure Email in Outlook: 3 Strategies

Email remains a dominant mode of communication in the business world, but with its ubiquity comes risk. In fact, a report from Verizon’s 2023 Data Breach Investigations revealed that 94% of malware is delivered via email. So what does this mean for IT professionals who manage sensitive communications or regulated data? That understanding security, and how to make it a core component of a broader security strategy, is a top priority. 

In this blog, we’ll explore how to send secure email in Outlook to safeguard organizational security and compliance. While there are multiple ways to secure email communication, the three methods outlined below are widely regarded as industry standards due to their proven reliability, ease of integration with Microsoft Outlook, and alignment with regulatory requirements. Let’s dig in.

Option 1: Enable Email Encryption

Enabling email encryption in Outlook ensures that your messages and attachments are protected, allowing only authorized recipients to view them. This is a critical feature for IT professionals managing sensitive communications in regulated industries such as healthcare, finance, or legal services. Below, we’ll guide you through the steps to enable email encryption in Outlook.

Note: Office just recently released Microsoft Copilot 365 which will replace Office features and programs. To that end, the above process may be subject to change.

Step 1: Choose the Right Encryption Method

Outlook supports two primary encryption methods:

  1. S/MIME (Secure/Multipurpose Internet Mail Extensions):
    • Requires a digital certificate issued by a trusted Certificate Authority (CA) such as  DigiCert, GlobalSign, or Entrust.
    • Ideal for organizations that already use certificate-based authentication.
  2. Microsoft 365 Message Encryption:
    • Available with Microsoft 365 Enterprise plans (E3, E5) or as an add-on.
    • Simplifies encryption for internal and external recipients, even if they don’t have certificates.

Step 2: Set Up S/MIME for Email Encryption

  1. Obtain a Digital Certificate:
    • Purchase or request a certificate from a trusted CA.
    • Install the certificate on your computer and associate it with your email account.
  2. Install the Certificate in Outlook:
  • Open Outlook.
  • Go to File > Options > Trust Center > Trust Center Settings.
    • Select Email Security.
    • Under Encrypted email, click Settings.
    • Choose your certificate under the Certificate and Algorithms section.
    • Click OK to save.

    3. Enable Encryption for Outgoing Emails:

    • In the same Email Security settings window, check the box for Encrypt contents and attachments for outgoing messages.
    • Optional: Configure Outlook to digitally sign all outgoing messages for added security.
    1. Send an Encrypted Email:
      • Compose a new email in Outlook.
      • Add recipients and content.
      • Click Options on the ribbon, then select Encrypt or Digitally Sign Message (depending on your setup).
      • Click send.

    Step 3: Set Up Microsoft 365 Message Encryption

    1. Verify Your Subscription:
      • Ensure your Microsoft 365 plan includes Message Encryption. Plans like Microsoft 365 Enterprise E3 or E5 generally support this feature by default. However, it’s always best to double-check with Microsoft’s official documentation or your specific plan details to be completely sure.
    2. Enable Encryption in Admin Settings:
      • Log in to the Microsoft 365 Admin Center as a global or security admin.
      • Go to Security & Compliance Center > Threat Management > Policy.
      • Configure rules to apply encryption to specific emails (e.g., emails with sensitive keywords or attachments).
    3. Send an Encrypted Email in Outlook:
      • Compose a new email in Outlook.
      • Go to the Options tab in the ribbon.
      • Click Encrypt and select the desired encryption level (e.g., Encrypt-Only, Do Not Forward).
      • Add your message content and send the email.

    Step 4: Verify Recipient Accessibility

    1. S/MIME:
      • Ensure recipients also have an S/MIME certificate and have exchanged public keys with you.
    2. Microsoft 365 Message Encryption:
      • Recipients without Microsoft 365 can view encrypted messages through a secure web portal. Ensure they follow instructions provided in the email.

    Step 5: Test and Monitor

    1. Test Encryption:
      • Send a test email to yourself or a colleague to verify the encryption setup.
        1. Protip: If you opt for the “encourage “email to yourself” option, we suggest using an email address that is different from the one that you’re sending from. Why? Sending encrypted emails to yourself can give false positive results. You automatically have your own certificate to decrypt.
      • Confirm the recipient can decrypt and view the email as expected.
    2. Monitor Security Logs:
      • Use the Microsoft 365 Security & Compliance Center to track encrypted email activity and ensure compliance with policies.

    Tips for Effective Encryption Management

    • Educate Users: Train your team on how to use encryption effectively, especially in regulated industries.
    • Update Certificates: Regularly renew and update S/MIME certificates to avoid disruptions.
    • Combine with Other Security Features: Pair encryption with multi-factor authentication (MFA) for enhanced security.
    PROSCONS
    Built-In Security: Native to Outlook and Microsoft 365, encryption ensures data confidentiality without requiring additional software, making it convenient for organizations already using Microsoft services.Recipient Compatibility Issues: Encrypted emails may require recipients to have specific tools, software, or certificates (e.g., S/MIME or a Microsoft 365 account). This can create challenges if the recipient is outside your organization or using unsupported software.
    Compliance with Regulations: Many industries, such as healthcare (HIPAA), finance (GLBA), and legal sectors, require encryption for email communication involving sensitive information. Outlook’s encryption methods help meet these standards.Complex Setup for S/MIME: Implementing S/MIME requires obtaining, installing, and managing digital certificates, which can be technically demanding, particularly for less experienced users.
    End-to-End Protection: Encryption ensures that only authorized recipients can decrypt and view the email content, reducing the risk of data breaches during transmission.Limited Features Compared to Third-Party Tools: Outlook’s native encryption is robust but lacks some advanced functionalities like detailed tracking, expiration controls, or easier access for external users, which are often provided by third-party tools (more on that option below). 

    Option 2: Use Secure Message Settings

    Microsoft Outlook provides built-in Secure Message Settings as an additional layer of control for safeguarding email communications. These settings focus on managing how recipients interact with emails, giving IT professionals and organizations granular control over sensitive content.

    How to Use Secure Message Settings in Outlook

    1. Enable and Configure Permissions:
      • In Outlook, compose a new email.
      • Navigate to the Options tab.
      • Click Permissions and select a setting like Do Not Forward or Encrypt-Only (depending on the required control level).
    2. Apply Sensitivity Labels:
      • Configure sensitivity labels in Microsoft 365 Admin Center.
      • When composing an email, apply the appropriate label to enforce compliance policies.
    3. Manage Sent Emails:
      • Use the Microsoft 365 Admin portal to modify or revoke permissions on emails if policies change or sensitive data is shared inadvertently.
    PROSCONS
    Granular Access Control: Features like “Do Not Forward” or “Read-Only” permissions allow senders to restrict how recipients handle email content, minimizing the risk of accidental or intentional data leaks.Limited to Microsoft Ecosystem: Advanced controls like “Do Not Forward” or Information Rights Management (IRM) require the recipient to use Outlook or another compatible Microsoft app. Users on unsupported platforms (e.g., Gmail) may encounter restrictions or usability issues.
    No Recipient Tool Dependencies: Unlike encryption, secure message settings don’t require recipients to have special software or tools, making them more versatile for external communications.Lacks Encryption-Level Security: Secure message settings control access but don’t encrypt the message. If intercepted during transmission, the content could still be exposed.
    Real-Time Updates: IT adminis can update or revoke permissions on already-sent emails if organizational policies change or if sensitive information is sent to the wrong recipient.No Protection Against Screenshots or Manual Sharing: While permissions can restrict forwarding or printing, they still don’t prevent recipients from taking screenshots or manually copying sensitive information.

    Option 3: Leverage Third-Party Tools

    Third-party tools offer enhanced features and flexibility for securing email communications in Outlook. While Microsoft Outlook provides robust native options, external tools can bridge gaps, add advanced capabilities, and streamline workflows for IT folks. 

    These tools integrate seamlessly with Outlook, providing a richer set of encryption, tracking, and access control options. Here’s how to use said tools with Outlook:

    Select the Right Tool

    • Evaluate tools based on organizational needs. Consider features like end-to-end encryption, ease of recipient access, and integration with DLP or other security systems.
    • Popular tools include Virtru, Zix, Proofpoint, and Mimecast.

    Integrate the Tool with Outlook

    • Install any necessary plugins or configure settings to enable integration with Outlook.
    • Most tools provide step-by-step installation guides and pre-configured settings for compatibility with Outlook.

    Configure Policies and Settings

    • Define organization-wide policies, such as automatically encrypting emails with certain keywords, or requiring secure delivery for specific domains.

    Test and Train

    • Run test scenarios to ensure the tool works seamlessly with Outlook.
    • Provide end-user training to help staff understand how to use the tool and securely access messages.

    Monitor and Maintain

    • Use the tool’s built-in analytics and reporting features to monitor email security and ensure compliance with internal and external policies.
    PROSCONS
    Enhanced Security Features: Tools like Zix, Virtru, and Proofpoint offer advanced encryption, policy enforcement, and secure delivery mechanisms that exceed Outlook’s native capabilities.High Cost: Many third-party tools require separate licensing, which can be a significant investment for organizations with tight budgets.
    Cross-Platform Compatibility: Third-party tools often work across multiple email clients, ensuring recipients can access secure messages regardless of their software or platform.Potentially Resource Heavy: IT teams and end-users may require resources such as additional training and onboarding to use the tool effectively, adding to implementation time and cost.
    Customizable Policies: Organizations can set granular security policies tailored to their industry or compliance needs, such as auto-encrypting emails containing specific keywords or sensitive attachments.Dependency on External Vendors: Organizations must rely on the vendor for updates, support, and troubleshooting, which can introduce risks if the vendor is unresponsive or discontinues the product.
    Integration with Data Loss Prevention (DLP): Many tools integrate with DLP systems to automatically identify and secure sensitive data before it leaves the organization.Integration Complexity: While most tools integrate seamlessly with Outlook, some may require configuration or adjustments to existing infrastructure, increasing initial setup complexity.
    Scalable and Enterprise-Ready: Designed to handle large-scale deployments, third-party tools are often better suited for enterprises with complex security requirements.Potential Overlap with Native Features: For organizations already using Microsoft 365’s encryption and security features, the additional functionality may not justify the cost.

    Elevate Your Email Security Strategy Today

    Mastering how to send secure email in Outlook isn’t just about technical know-how — it’s about protecting your organization from potential data breaches and regulatory fines. From configuring encryption to troubleshooting common issues, IT professionals must take a proactive approach to email security to ensure sensitive communications remain private and compliant.

    These strategies — built-in encryption, secure message settings, and third-party tools — are designed to accommodate different organizational needs, ranging from small businesses to enterprises with stringent security requirements. While alternative options exist, such as manual encryption workflows or niche tools, they often introduce complexities or lack the seamless compatibility with Outlook that IT professionals require. By focusing on these three methods, we aim to provide actionable, efficient, and trusted solutions for securing your communications.


    Bobby Amos, Syncro