E-mail Certificates: Firefox / Thunderbird

May 25, 2018 in Windows and Email S MIME

How to collect and install Comodo e-mail certificates for Mozilla Firefox and Thunderbird


  1. Check your email on the email address that you applied with.
  2. Note: Make sure you use the same browser you applied with!

Install (part 1 of 2)

  1. Click the button that says 'Click & Install Sectigo Email Certificate'.
  2. Note: If that does not open in the same browser as you applied on please follow the directions underneath the button.
  3. You will see a message stating that your certificate is being installed. Do not close window!
  4. A message will be displayed that your certificate was installed successfully.

Installation into Thunderbird (Mail Client)

  1. Export to PFX File
  2. Inside Firefox go to Tools -> Options (Windows), Edit -> Options (*nix), Firefox -> Options (Mac)
  3. Then go to Advanced -> General -> Encryption and click on 'View Certificates'.
  4. Select the tab that says 'Personal' or 'Your Certificates'.
  5. Highlight the certificate that expires on 1 year from when you applied for your certificate.
  6. Once highlighted select the button that says 'Backup'.
  7. Next one should be prompted to save the file.

* Save location: Desktop
* File Name: email address; Ex: [email protected] would become support_sectigo_com
* File type: PKCS12 Files (*.p12)

8. Provide a password for your .p12 file.
9. Click 'Save'

Import/Install to Thunderbird (part 2 of 2)

  1. Inside Thunderbird go to 'Tools -> Account Settings' and select 'Security' under the e-mail account you applied with.
  2. Click on 'View Certificates' to load the Thunderbird Certificate Manager.
  3. Click 'Import' and supply the password you created above.
  4. Close the Certificate Manager.
  5. Click 'Select'.
  6. Select your certificate from the drop-down menu and click 'OK' when finished.
  7. Perform the above step for both the Digital Signing and Encryption.
  8. note: If you wish to digitally sign every message, please select the option 'Digitally Sign Messages (by default)'
  9. Click 'OK' to exit the 'Account Settings' window.
  10. Now your certificate is installed ready to use within Thunderbird!

Note: To Encrypt a message, click the down arrow to the right of the 'Security' button.