How to Import an S/MIME Email Certificate into Thunderbird

This document provides detailed instructions on importing an S/MIME email certificate into Thunderbird, broken down into the following steps:

1. Open Account Settings

1. Launch the Thunderbird email client.
2. Click the three-dot icon in the top-right corner to expand the menu, then select Settings.

3. On the Settings page, click Account Settings in the bottom-left corner.

2. Navigate to End-to-End Encryption Settings

In the left sidebar menu of the Account Settings interface, click End-To-End Encryption.

3. Manage S/MIME Certificates

Click Manage S/MIME Certificates to open the Certificate Manager window.

4. Import the Certificate File

1. In the pop-up window, click Import.
2. Select the .pfx certificate file you requested (usually located in the IIS folder).
3. Enter the password for the .pfx file (the password is typically stored in the same folder as the .pfx certificate; open the password.txt to view it).

4. Click 【OK】 to complete the certificate import.

5. Bind the certificate to your email account

1. Return to the account settings page, and click 【Select】 in the Personal Digital Signing Certificate section.
2. The pop-up dialog will display the certificate you just imported. Click 【OK】 to bind it to your email account.

3. Click 【Yes】 on the pop-up confirmation page.

4. The certificate is bound successfully.

6. Send signed or encrypted emails

On the menu bar of the new email composing page, click 【S/MIME】, and you can select from the drop-down menu:

• Send Signed Email: Digitally sign the email so that the recipient can verify the email source and integrity.
• Send Encrypted Email: Encrypt the email content using the recipient's public key.

Note

If you need to send an encrypted email, the recipient must first send you a signed email. You can only send an encrypted email to them after you have obtained their public key.