"Nigel J. Andrews" <nandrews(at)investsystems(dot)co(dot)uk> writes:
> Doesn't that just force the delivering system to send the spam through your
> secondary server?
A 500-series error isn't supposed to be retried is it?  But in any case,
I run the same filters on my secondary server.  Both the IP and the HELO
checks would be quite useless if I used an MX that wouldn't support 'em.
			regards, tom lane