Thursby Software Systems (http://www.thursby.com/) has announced secure Apple email support for US government workers in the latest version of its PKard for Mac software.
 
In Mac OS X 10.7 (“Lion”), there’s no native smart card support. Smart cards are required to handle basic tasks like access to secure web portals and email, mandated by Homeland Security Presidential Directive 12, or HSPD-12   Previous OS X versions had partial support, covering older smart cards only.   

PKard 1.1 adds secure mail signing, encryption and decryption in Apple Mail to the existing Apple Safari and Google Chrome secure web and web VPN access that cover all CAC and PIV smart cards. The update to PKard for Mac is free for existing users and pricing remains at US$29.95 for new users.