Wietse Venema: > > Problem 2) My smarthost is only smart enough to try sending to one other > > relay (I think). > > If the machine sends mail to a less preferred MX host than itself, > then it is badly borked. To pull that off with Postfix you would > have to turn off DNS or override the routing with a transport map.
... or override routing with relayhost. So yes, a backup MX server should not use a relayhost unless it also has a transport map to send mail to the primary MX. Wietse