OSX Mail - Installation and use of a Digital Signature

Digital Signature Installation

As soon as the certificate is ready, an email will be sent with a link to the download section of the SSL Certificates website. Here you can find a button to download the certificate. Once the certificate has been downloaded, it can be installed by double-clicking on it: Keychain access will start and ask if the certificate should be installed. Clicking Yes will complete the installation.

Set the Digital Signature

If the e-mail address in the certificate matches the e-mail address in Mail and the installation is successful, Mail is also immediately ready to use the certificate. By restarting Mail and then creating a new message, these settings become visible. At the far right, just above the subject, two extra buttons appear: one with a lock and one with a black gear with a white check mark in it. The lock indicates whether the message is sent encrypted or not; the gear indicates that the e-mail is digitally signed.

It is possible that the lock is gray and cannot be pressed. In that case the message cannot be encrypted. To be able to encrypt a message, the e-mail certificate of the addressee is required: the addressee must already have a digital signature and must have sent a digitally signed e-mail to the sender. When the sender has added the e-mail address of the addressee as a contact person in the address book, the digital signature of that person is also automatically saved. From that moment it can be used to send encrypted messages.

Check whether the Digital Signature is installed

With Keychain Access you can check if the digital signature is installed correctly:

1. Open Finder and go to Programs → Utilities and double-click Keychain Access.
2. Click on Certificates in the left panel. An overview appears with all installed certificates in the right panel.
3. Double-click on the certificate to be checked to view the details. If there is a green check mark at the top, the certificate is valid. Here you can also check the e-mail address of the certificate under the Details heading.