How can I implement my email certificate (S/MIME) in Mac OS X Mail / Apple Mail and sign/encrypt my email?

We recommend using a Firefox browser on a Mac OS to request and retrieve the certificate. If you have already retrieved the certificate, please make sure that you have the certificate in PKCS12 format. If not, please export the certificate from the Firefox browser to PKCS12 format. Instructions can be found in our FAQ entry "How can I export an e-mail certificate (S/MIME) from Firefox?"
If your certificate is not yet installed on the computer you are using, please export it from the computer on which it is located. You must then transfer it to this computer (email it to yourself or save the certificate file to USB and then copy it over). You can then follow the "Import" instructions in this document. Here are some instructions that you can use for exporting.

Import your certificate into your Apple Mail

1

Apple Mac OS uses Keychain Access to manage digital certificates. To import the certificate into Apple Mail, click Applications > Utilities and open Keychain Access.

2

Under "Keychains" please select "login" and under "Category" please click on "My Certificates". Now click on "File" and select "Import Items".

3

Now select the certificate file that you have previously exported from Firefox and enter the password.

If you are asked whether you should automatically trust certificates issued by your CA, select the "Always trust" option to trust your certificate and install it.

4

The certificate is now installed and can be viewed under Category > My Certificates. Once the installation is complete, messages can be signed and/or encrypted using Mac Mail or Appple Mail.

Signing and encryption of messages

Signing an email ensures that the recipient knows that the email came from you and informs them that it was not modified during transmission.
Encrypting an email ensures that only the recipient can read the content and attachments of the email.

To encrypt e-mails, you must first have the recipient's e-mail certificate in your certificate store. To obtain the recipient's certificate, first ask the recipient to send you a signed e-mail. When you receive the signed e-mail, his certificate is automatically imported into your certificate store and you can then send an encrypted e-mail to that person.

Digitally sign a message

1

Open a new message and write down your text as usual.

2

To digitally sign a message, click the "Sign" icon, which is displayed in the same window.

3

If you only want to digitally sign the message, you can now send it. If you would like to encrypt the message and its attachment as well, continue with the following step before sending it.

Encrypting a message

1

Open a new message and write down your text as usual.

2

To encrypt the message, click on the "lock" symbol, which is displayed in the same window.

3

If you only want to send the message encrypted, you can now send it. If you want to digitally sign the message, please follow the instructions in the previous step before sending it.