Relay host question - ReadList.com

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Relay host question
\ Maier,Chris (30 Aug 2007)
. \ Noel Jones (30 Aug 2007)

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Subject:	Relay host question
Group:	Postfix-users
From:	Maier,Chris
Date:	30 Aug 2007

Is there a way to specify multiple relay hosts in the main.cf file?
Is there another way to specify multiple hosts for a default outbound
transport?

We run split brain DNS here, so there are two possible sets of servers
that may be returned for MX DNS queries for "heb.com". My Postfix
servers are serving as the central internal mail router (smart host), so
the Postfix servers are the MX (internally) for my "heb.com" domain.

What I need to do is ensure that my outbound relay email goes through
one of our three external mail gateways, but the Postfix servers are on
the internal network and must query the internal DNS MX records, so I
can't simply point to "heb.com" as my relay host/domain because I would
be creating a mail routing loop. Having all three upstream servers
configured as relay hosts is required because each of the external
servers is connected to one each of our three data providers. If one of
the WAN links goes down, the network team disables port 25 to the
affected link/external gateway thereby forcing mail to use an alternate
path (and NOT queue for long periods of time).

So, is there some way that I can create an equivalent to:

relayhost = [ext1.heb.com ext2.heb.com ext3.heb.com]

I know of some possible answers that don't involve Postfix, but I'm
hoping there is a Postfix based solution. Asking for more hardware and
having the network team configure it to accommodate my needs is a last
resort IMHO.

Thanks,
Chris