May 8 15:50:28 s8 postfix/smtpd[5603]: NOQUEUE: reject: RCPT from localhost[::1]: 454 4.7.1 <szab...@gmail.com>: Relay access denied; from=<mailman-boun...@hostlocal.com> to=<szab...@gmail.com> proto=ESMTP helo=<s8.hostlocal.com>
Seems like the ipv6 loopback address is not part of mynetworks.
