>but now I need to deliver to a different host if 1.2.3.4 is not >available - just like a secondary MX record. > >Will transport work with two entries like: >example.com smtp:[1.2.3.4] >example.com smtp:[9.8.7.6] >and fail over to the second if the first is not available.
I don't think that will work, postmap will insist on only one, the first one, and complain not-fatally about duplicate. >If not, any ideas on how can this be setup? These hosts may >not be in the same location and may even be split between >Private IPs and Public IPs. resolution via will bring the traffic to IMGate and then be resolved in transport.map: example.com smtp:mxx.yourchoice.com postfix will query DNS for mxx.yourchoice.com. Without the [domain] brackets, postfix queries for the MX records. from man 5 transport: "The interpretation of the nexthop field is transport dependent. In the case of SMTP, specify a service on a non-default port as host:service, and disable MX (mail exchanger) DNS lookups with [host] or [host]:port. The [] form is required when you specify an IP address instead of a hostname." Then you choose yourchoice.com under your DNS control: mxx.yourchoice.com mx 5 a.somewhere.com 10 b.somewhere.com etc 1.somewhere.com. A ip.ad.re.s1. 2.somewhere.com. A ip.ad.re.s2. I haven't done this, but that's how I would try it. Len