Enabling Client Certificates for iOS Mail


Enabling these options will allow you to digitally sign  and encrypt all email sent from your device.

  1. Go to Settings > Mail, Contacts, Calendars.

  2. Select the email account associated with your Client Certificate.

  3. Tap the Account button with your email address.

  4. On the Account screen, change the "S/MIME" setting to ON. The "Sign" and "Encrypt" options are off by default.

    • To enable signing, tap Sign, and then select your certificate. This will digitally sign every email you send from your email account on this device.

    • To enable encryption, tap Encrypt, and then select your certificate.


      Note:       The encryption option will attempt to encrypt all correspondence from your iOS device. If you do not have the public certificate for a recipient, the email message will not be encrypted.

You also read Apple's knowledge-base article related to this here:
http://support.apple.com/kb/HT4979