There is new version of courier mail server, 0.53.2. It fixes vulnerability published as CVE-2006-2659.
Fix: mail# diff -u Makefile Makefile.new
CATEGORIES= mail ipv6
mail# diff -u distinfo distinfo.new
Awaiting maintainers feedback
Committed, with changes. I fixed pkg-plist and added a patch to build
fine on FreeBSD 4.x. Thanks!