How to Implement Email Signing Certificates for Encrypted Communication March 3, 2025

Email signing certificates are essential for securing email communications by encrypting messages and verifying sender authenticity. Implementing these certificates enhances data privacy, prevents phishing attacks, and ensures email integrity.

Prerequisites:

• A valid email signing certificate (issued by a trusted Certificate Authority like DigiCert, Sectigo, or GlobalSign).
• Access your email client (e.g., Outlook, Thunderbird, or Apple Mail).
• Basic knowledge of email configuration settings.

Steps to implement Email Signing Certificates:

1. Obtain an Email Signing Certificate:
   1. Purchase or request an email signing certificate from a Certificate Authority (CA).
   2. Download the certificate after successful validation.
2. Install the Certificate on Your System:
   1. For Windows:
      1. Open the Certificate Manager by typing certmgr.msc in the Windows search bar.
      2. Import the certificate under Personal > Certificates.
      3. Follow the on-screen instructions to complete the installation.
   2. For macOS:
      1. Open Keychain Access.
      2. Drag and drop the certificate into the Login keychain.
      3. Authenticate if prompted.
3. Configure Email Client to Use the Certificate:
   1. Outlook:
      1. Open Outlook and go to File.
         
      2. Click on Options.
         
      3. Select the Trust Center.
      4. Click on Trust Center Settings > Email Security.
         
         
      5. Under Encrypted email, click Settings.
         
      6. Select the installed certificate under Signing Certificate.
      7. Enable Digitally signed outgoing messages.
      8. Click OK to save the settings.
         
   2. Thunderbird:
      1. Open Thunderbird and go to Preferences > Privacy & Security.
      2. Under Certificates, click View Certificates.
      3. Import the email signing certificate.
      4. Enable Digitally signed messages by default.
4. Test the Certificate:
   1. Send a test email to yourself with digital signing enabled.
   2. Verify that the email is labelled Digitally Signed in the recipient’s inbox.
   3. Optionally, test encryption by exchanging signed emails with a trusted contact.
5. Renew and Manage Certificates:
   1. Regularly check the certificate’s expiration date and renew it as needed.
   2. Keep backup copies of certificates for security purposes.

Implementing signing certificates ensures secure and authenticated communication. By following the steps above, you can protect your emails from unauthorised alterations and improve overall email security.

For a complete security setup, learn How to install an SSL certificate for a domain in Plesk