Table of Content

1. Installing the S/MIME Certificate
1-1. Prerequisites
1-2. Install Procedure  
2. Sending Digitally Signed E-mails
2-1. How to Send Digitally Signed E-mails
2-2. How to Confirm a Sent E-mail That Was Digitally Signed 
3. Replacing the Expiring S/MIME Certificate with A New Valid One
3-1. Prerequisites
3-2. How to Install the Replacement

1. Installing the S/MIME Certificate

1-1. Prerequisites

The prerequisites for using the S/MIME Certificate in Apple Mail are described.
Replace the technical terms according to the user environment in which the S/MIME Certificate will be used.
(The procedures required for Apple Mail 11.2 on macOS 10.13.3 (High Sierra) are described in this document.)

1-2. Install Procedure

2. Sending Digitally Signed E-mails

2-1. How to Send Digitally Signed E-mails

How to Send Digitally Signed E-mails

1. Select [File] > [New Message].
   
   
   
2. In the new message screen, focus on the digital signature icon to make sure that the signature is enabled.
   
   
   
3. Click the Send icon when the message is complete.
   
   
   
4. If you get the password prompt for the keychain and the access permission, enter the password used for the certificate install and select [Allow].
   
   
   Note: If [Always Allow] is selected, the keychain access prompt will not appear each time. 
   
   This completes sending digitally signed e-mails.

2-2. How to Confirm a Sent E-mail That Was Digitally Signed

How to Confirm a Sent E-mail That Was Digitally Signed

1. Select a sent e-mail that was digitally signed from the [Sent] folder.
   
   
   
2. Click on the [Signed] icon.
   
   
   
3. Make sure that the certificate is marked as trusted, and click [OK].
   
   
   This completes confirmation of a sent e-mail that was digitally signed.

3. Replacing the Expiring S/MIME Certificate with A New Valid One

The procedure to install an updated S/MIME is as follows.

3-1. Prerequisites

Replace the technical terms according to the user environment in which the S/MIME Certificate will be used.
(The procedures required for Apple Mail 11.2 on macOS 10.13.3 (High Sierra) are described in this document.)
Care must be fully used for a case that the S/MIME could be marked as expired (Note 1) even before the expiration unless this installation is performed.

Note 1: When a digitally signed e-mail is received by other MUAs than the Mac mail.app,
it is known that the e-mail sent on the day before the certificate expiry could be marked as expired unexpectedly in some cases.

3-2. How to Install the Replacement

Procedure to Replace the Expiring Certificate

1. Select [Keychain Access] in the [Utilities] pane.
   
   
   
2. In the Keychain Access screen, select the old, expiring but currently used S/MIME Certificate from the certificate list, and press the [Delete] key on the keyboard.
   Note: Be sure to carefully check expirations before deleting so as not to select a new, updated S/MIME by mistake.
   
   
   
3. Enter the keychain password and click [OK].
   
   
   
4. Reconfirm that you want to delete the old, expiring S/MIME Certificate, and click [Delete]. 
   
   
    This completes replacing the expiring S/MIME Certificate with a new valid one.