On Fri, 2008-03-28 at 17:54 +0100, Searcher wrote: > So I just want a simple MX check (if the incoming IP is the MX for the
> domain)
...which won't get you much; many operations use a completely different
set of IP addresses at least, if not machines, for outbound messages as
compared to inbound.
An MX record is only useful in that it indicates where you need to send
mail for a given domain. It signifies nothing with regard to messages
coming from a given domain, so to filter/whitelist on it alone is, well,
perhaps not wise.
