We've run into a problem which is only getting worse; spammers are bypassing our spam appliance, which sits in front of our CiommuniGate Pro server. The only MX Record for our domain points to the appliance, so I'm guessing that these spammers are not performing MX lookups.
We have mobile users we need to support.. we allow them to authenticate against the server, and they are then treated as Client IP's. So we can't lock down SMTP to only accept connections from the appliance.
I realize this isn't really an IronPort problem... the appliance has been incredible, but out users don't "get" it. They're getting spam, so they think something is wrong with the appliance.
Has anyone else here run into this problem? What have you done? Is there something I'm not thinking of which might thwart these spammers?
Thanks for any thoughts,