Handling multiple relay destinations

I'm trying to set up a mail gateway with postfix, which will sit in our
DMZ and just forward all mail through to our internal servers.

I'm putting the domain name in relay_domains and then the internal
server name in the transport file, specified by transport_maps. The
problem I have is that I want postfix to use more than one destination
for relaying, to guard against failure of one of the internal machines.
The syntax:

example.com smtp:[internal_mail.example.com]

only allows me to give one server.

Is there a way of giving multiple servers here, and having postfix
either 'load balance' between them or use the second if the first
fails?

I realise that I could omit the '[]' and using MX lookups, but this
would mean getting custom MX records to the gateway machine, which I'm
not keen on.

Thanks for any help

The transport file can't handle multiple result values.

Per the Postfix author on December 9, 2005:

I am revising the SMTP client connection management code, and it
is so ridiculously complicated that there will not be multi-nexthop
support in the forseeable future.

Wietse

Sure would be nice though.

--
Greg



Adam wrote:
> I'm trying to set up a mail gateway with postfix, which will sit in our
> DMZ and just forward all mail through to our internal servers.
>
> I'm putting the domain name in relay_domains and then the internal
> server name in the transport file, specified by transport_maps. The
> problem I have is that I want postfix to use more than one destination
> for relaying, to guard against failure of one of the internal machines.
> The syntax:
>
> example.com smtp:[internal_mail.example.com]
>
> only allows me to give one server.
>
> Is there a way of giving multiple servers here, and having postfix
> either 'load balance' between them or use the second if the first
> fails?
>
> I realise that I could omit the '[]' and using MX lookups, but this
> would mean getting custom MX records to the gateway machine, which I'm
> not keen on.
>
> Thanks for any help
>