How to Encrypt and Secure Email Messages in Outlook Mail Client

Sending sensitive information by email carries risks. Email messages sent using regular SMTP protocols are transmitted in plain text, which means they can be easily read by hackers and cyber criminals. Fortunately, you can take steps to encrypt your Outlook email messages to improve security.

Why Email Encryption is Important

Here are some key reasons why you should consider encrypting sensitive email communications:

  • Privacy – Encryption prevents unauthorized people from being able to read the contents of your messages during transmission or if emails are intercepted. This helps protect private communications.
  • Data security – Encryption provides an essential layer of protection for sensitive information like financial data, health records, trade secrets, and other confidential data. This helps prevent costly data breaches.
  • Compliance – Some industry compliance regulations like HIPAA require the use of encryption for emails containing sensitive data. Encryption helps organizations meet compliance obligations.

Outlook Email Encryption Options

There are two main methods available for encrypting Outlook email messages:

1. Use S/MIME for Digital Signatures and Encryption

S/MIME (Secure/Multipurpose Internet Mail Extensions) is an encryption standard supported by Outlook. With S/MIME, you can digitally sign messages to verify your identity and encrypt messages to protect contents.

To use S/MIME:

  • Obtain an S/MIME certificate issued by a trusted certificate authority
  • Install the certificate in Outlook and enable S/MIME
  • Digitally sign outgoing messages and encrypt sensitive messages

S/MIME encryption works seamlessly with other S/MIME-enabled email clients like Outlook, Gmail, etc. However, the recipient’s email service and client must support S/MIME to decrypt messages.

2. Enable Office 365 Message Encryption

If you use Microsoft 365 or Office 365 for email, you can take advantage of built-in Office 365 Message Encryption. This allows you to easily encrypt messages and set access restrictions.

To enable Office 365 Message Encryption:

  • Microsoft 365 E3 and E5 plans include message encryption capabilities
  • Configure encryption rules in the Office 365 Security & Compliance Center
  • Set up authentication methods for recipients to access encrypted messages

Office 365 Message Encryption provides seamless encryption between Office 365 users. It also allows you to securely send encrypted emails to people outside your organization.

Best Practices for Securing Outlook Emails

Along with encryption, follow these security best practices:

  • Always think before clicking – Be wary of email attachments and links which are common vectors for attacks. Never click suspicious links or attachments.
  • Create strong passwords – Use complex passwords and enable multi-factor authentication for your Microsoft account to prevent unauthorized access.
  • Back up your data – Regularly back up your Outlook data files to prevent loss of emails. Store backups securely using encryption.
  • Install security updates – Keep your Windows OS and Outlook client updated with the latest security patches. Enable auto-updates where possible.


Email encryption is vital for securing sensitive communications against growing cybersecurity threats. By enabling S/MIME or Office 365 encryption capabilities, Outlook users can securely exchange confidential information and ensure regulatory compliance. Combined with protective measures like secure passwords and backups, encryption provides comprehensive protection of your inbox.