>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
