Dovecot in Apple Mac OS X 10.6.5 10H574 does not properly manage memory for user names, which allows remote authenticated users to read the private e-mail of other persons in opportunistic circumstances via standard e-mail clients accessing a user's own mailbox, related to a "memory aliasing issue." Per: http://lists.apple.com/archives/security-announce/2010//Nov/msg00001.html
'Dovecot is only provided with Mac OS X Server systems. This issue only affects systems running Mac OS X Server v10.6.5 (10H574). This issue does not affect the Dovecot open source project.'