Encrypt email messages using S/MIME in the new Outlook for Mac

When you need to protect the privacy of an email message, encrypt it. Encrypting an email message in Outlook means it's converted from readable plain text into scrambled cipher text. Only the recipient who has the private key that matches the public key used to encrypt the message can decipher the message for reading. Any recipient without the corresponding private key, however, sees indecipherable text.

To use S/MIME encryption, the sender and recipient must have a mail application that supports the S/MIME standard. Outlook supports the S/MIME standard.

Send an encrypted message with S/MIME

Before you start this procedure, you must first have added a certificate to the keychain on your computer. For information about how to request a digital certificate from a certification authority, see Mac Help. You must also have a copy of each recipient's certificate saved with the contacts' entries in Outlook.

If your recipient is listed on an LDAP directory service, such as the global address list (GAL) used by Microsoft Exchange Server, the recipient's certificate is published to the directory service and available to you together with other contact information.

If your recipient is listed on an LDAP directory service, the recipient's certificate is published to the directory service and available to you together with other contact information.

  1. Choose Outlook and select Preferences.

  2. Select the account that you want to send an encrypted message from and select Security.

  3. In Certificate, select the certificate that you want to use. You'll only see those certificates that you've added to the keychain for your Mac OSX user account and those certificates that are valid for digital signing or encryption. To learn more about how to add certificates to a keychain, see Mac Help.

  4. Choose OK, and then close the Accounts dialog box.

  5. In a message, choose ... menu and select S/MIME > Encrypt with S/MIME.
    Encrypt with S/MIME

Tip: If you don't see S/MIME under the ... menu, select Customizable Toolbar and add S/MIME to the toolbar.

6.  Finish composing your message, and then click Send.
 

Note: When you send an encrypted message, your recipient's certificate is used to encrypt his or her copy of the message. Your certificate is used to encrypt the copy that is saved to your Sent Items or Drafts folder in Outlook.

Send a digitally signed message

Before you start this procedure, you must have added a certificate to the keychain on your computer. For information about how to request a digital certificate from a certification authority, see Mac Help.

  1. Choose Outlook and select Preferences.

  2. Select the account that you want to send an encrypted message from and select Security.

  3. In Certificate, select the certificate that you want to use. You'll only see those certificates that you've added to the keychain for your Mac OSX user account and those certificates that are valid for digital signing or encryption. To learn more about how to add certificates to a keychain, see Mac Help.

  4. Do any of the following:

    To make sure that your digitally signed messages can be opened by all recipients, even if they do not have an S/MIME mail application and can't verify the certificate, select Send digitally signed messages as clear text.

    To allow your recipients to send encrypted messages to you, make sure that you've selected your signing and encryption certificates, and then select Include my certificates in signed messages.

  5. Choose OK, and then close the Accounts dialog box.

  6. In a message, choose ... menu and select S/MIME > Add digital signature.

    Tip: If you don't see S/MIME under the ... menu, select Customizable Toolbar and add S/MIME to the toolbar.

  7. Finish composing your message, and then click Send.

See Also

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