For years we have run multiple MX records, and for years viruses in particular have targetted the secondary MX as an easier way into the enterprise, on the theory that the security defences on a backup route may be weaker. We have also noticed when our primary MX path is down, some mail servers - that should know better - don't swap to the secondary MX, and when the primary MX path comes up again, lo and behold fresh mail arrives. Spammers, never slow to pick up on any technique, are also likely to be aware of the nolisting technique, so I would say any relief is likely to be temporary. In short, I'd suggest using a good spam filtering tool with good reporting, so you are aware of what is going on. This is what we have used with great success: http://www.barracudanetworks.com Jeremy +64 21 990 177 Jeremy(a)Strachanconsulting.co.nz