Apple Mail.app 3.5 on Mac OS X, when βStore draft messages on the serverβ 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.
enablesecurity.com/2008/10/03/apple-mailapp-security-advisory/
resources.enablesecurity.com/advisories/apple-mailapp-smime.txt
securityreason.com/securityalert/4363
www.securityfocus.com/archive/1/497057/100/0/threaded
www.securityfocus.com/bid/31598
www.securitytracker.com/id?1021019
exchange.xforce.ibmcloud.com/vulnerabilities/45688