How to install S/MIME

Step 1: import the Certificate

  1. After you receive the certificate from the CA, follow their instructions to download it to your computer. This usually comes as a .p12 file.
  2. double-click the certificate file and follow the wizard to import it.

Step 2: install the Certificate in Windows

  1. Open Windows Certificate Manager; 
  2. press Windows + R;
  3. type certmgr.msc
  4. press Enter. This will open the Certificate manager; 
  5. navigate to Personal > Certificates; 
  6. right-click on the empty space, select All Tasks > Import; 
  7. use the wizard to browse to the location of your .p12 Certificate file; 
  8. you will need to enter the password provided when you received the Certificate. 

Once imported, the certificate should appear under Personal > Certificates with your name or email address.

Step 3: configure S/MIME in Microsoft Outlook

  1. Open Outlook: launch Microsoft Outlook on your desktop; 
  2. go to Trust Center Settings. Click on File in the top-left corner;
  3. select Options from the left-hand menu;
  4. in the Options window, go to Trust Center and click Trust Center Settings;
  5. in the Trust Center window, select Email Security; 
  6. under the Encrypted Email section, click Settings; 
  7. in the Settings window, under Certificates and algorithms, select the Choose button next to Signing Certificate; 
  8. select the S/MIME Certificate from the list (the one you just imported); 
  9. make sure the same Certificate is selected under Encryption Certificate; 
  10. choose encryption and hashing algorithms if required (typically RSA for signing, AES for encryption). 

 

Enable digital signatures and encryption (optional):

  1. if you want to always sign your emails, check the box that says Add digital signature to outgoing messages; 
  2. for encrypting emails by default, check Encrypt contents and attachments for outgoing messages; 
  3. click Ok to save your changes and close the dialog boxes.

The recipient needs an S/MIME certificate and the correct configuration in their email client to open encrypted messages.

This guide should help you configure S/MIME certificates in Microsoft Outlook. If you're using Outlook for Office 365, the steps are very similar, but the user interface may vary slightly depending on the version.

Step 4: test the S/MIME Configuration

  1. Create a new email. In the Options tab of the message, click the Sign icon (it looks like a pen); 
  2. compose and send the email.

Send an encrypted email (optional):

  1. to send an encrypted email, you must have the recipient’s public key (which they usually send to you in a signed email). Open a new email, go to the Options tab, and click Encrypt; 
  2. compose and send the encrypted message.

Public Keys are shared through digitally signed emails. When someone receives a signed email, they automatically receive your public key.

Make sure both sender and recipient use email clients that support S/MIME (Outlook, Apple Mail, etc.).

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