Apple Mail.app 3.5 on Mac OS X, when "Store draft messages on the server" is enabled, stores draft copies of S/MIME email in plaintext on the email server, which allows server owners and remote man-in-the-middle attackers to read sensitive mail.
https://exchange.xforce.ibmcloud.com/vulnerabilities/45688
http://www.securitytracker.com/id?1021019
http://www.securityfocus.com/bid/31598
http://www.securityfocus.com/archive/1/497057/100/0/threaded
http://securityreason.com/securityalert/4363
http://resources.enablesecurity.com/advisories/apple-mailapp-smime.txt
http://enablesecurity.com/2008/10/03/apple-mailapp-security-advisory/