Duane Hill wrote on Sat, 25 Aug 2007 22:29:50 +0000 (UTC): > What happens if the remote MX is within a private IP range? Should I > accept that message, knowing fully, the recipient would never be able to > respond?
This feature looks fine on first glance, but on second I think this is dangerous if it gets applied to all MX positions. For instance the two MX setup where one machine is behind a firewall and a gateway machine is first MX and forwards to the machine behind the firewall. This is an accepted setup. Couldn't I achieve the same thing without a firewall? The first MX gets another IP from a private range and the second is on private only. So, it's not reachable from outside, but the first MX can forward to it. "backup MXs (that don't exist)" doesn't mean a private range. You simply set it to an IP that doesn't have SMTP or one that points to nirvana, but still a valid public IP address. I don't use that technique and don't think I will need to use it in the near future, but I can't see anything bad in it, sorry. As John says only spammers or broken MTAs should have a problem with that. I also agree on SAV with John, it's almost as worse as challenge-response mechanisms. Kai -- Kai Schätzl, Berlin, Germany Get your web at Conactive Internet Services: http://www.conactive.com
