Add a recipient's certificate to your contact list

Open a digitally signed message from the recipient.
Right-click the name in the From box, and then click Add to Contacts on the shortcut menu.
If you already have a contact entry for this person, select Update new information from this contact to the existing one.

Notes

To view the certificates for a contact, in the Contacts folder, double-click the person's name to open the contact, and then click the Certificates tab.
You can also import someone's certificate (.cer) file into Microsoft Outlook when viewing the Certificates tab by clicking Import. You usually do this when someone sends you their certificate as an attachment.