Override MX records and round-robin

[Edward Hibbert]

Hi all,

New to this list, so apologies if I breach etiquette.

I am having trouble send email to a company that should know better. It exposes a single MX record, which appears to front a pool of real servers, and select which one to use based on the IP connecting to the pool. It is a sadly regular occurrence for some of those servers to be very badly broken and take many days or weeks to be fixed. During this period they return 451 errors to almost all requests.

I would like to override the MX record that they publish and send directly to the members of the pool, in such a way that if we're getting 451 errors, we try other servers. That way, as the individual servers break (as they will) we'll automatically use one of the others.

I appreciate this is an outrageous hack and vulnerable to changes in their mail server topology.

At the moment I'm using a simple transport map which overrides the MX as follows:

/^.*@domain.*%/ smtp:[single host]

I would like to be able to add multiple hosts in there, which get retried in the event of 451 errors.

I'm no postfix expert; can anyone advise?

Thanks,

Edward