• Make IPV6 optional

On system without any IPv6 addresses emailrelay fails to start with messages:

service emailrelay start

emailrelay: error: cannot bind the listening port: :::25
emailrelay: exception: cannot bind the listening port: :::25
/usr/local/etc/rc.d/emailrelay: WARNING: failed to start emailrelay

PR: 204126
Submitted by: Dmitry Afanasiev
Approved by: maintainer timeout