Flaw bug created to hold information about an old flaw we knew something about. For more details see the MITRE CVE description.
MITRE description: Postfix 2.1.3, when /proc/net/if_inet6 is not available and permit_mx_backup is enabled in smtpd_recipient_restrictions, allows remote attackers to bypass e-mail restrictions and perform mail relaying by sending mail to an IPv6 hostname.