MR> It could be useful for IPv4-only nodes if the INO4 flag is used by a MR> ruleset in the mailer configuration, for example:
MR> if IBN & !INO4 : "call using binkp"
MR> The node might running dual stack inside the LAN but only got IPv4 MR> Internet access.
FYI, any node with ipv4 MAY connect to IPv6 world using "6to4" tunnel or teredo or tunnel brocker. IPv6 on my node connected via 6to4 (address in the subnet 2002::)