allow only authenticated access to qmail

[wmchurch]

Here's my scenario.

I have a Plesk 7.5.4 server that sits behind an IronPort mail appliance.

I want all SMTP mail destined to the hosted Plesk domains to go through the IronPort, so I changed all the mx records so that the IronPort is the only mail server for every domain. I've verified this several different ways (mx lookups, named files, etc...) this is done.

However, I still get people sending mail directly to the Plesk server either by cached lookups or maybe just spammers targeting the server directly. In any event I want to restrict SMTP access on the Plesk server to only authenticated users (either via SMTP AUTH or pop before smtp) and disallow any direct SMTP from outside servers other than the IronPort (which will come from a specific IP address and network interface).

So here's my problem, I can't just shut off or firewall SMTP on the Plesk because users won't be able to send mail. And I'll need to be able to accept mail from the IronPort somehow so I'd need to setup an additional listener on a specific IP or port.

I find qmail's configuration to be frustrating at best, tried a few options but nothing seems to do what I need.

Seems like a simple task to me, so any ideas?

Thanks in advance,
Bill