Using SMTP for incoming mail

[#1]

I've got my Plusnet email set to forward to my IP address where I've got a server running a pretty locked down version of postfix.
I'm getting a lot of attempts from China, Korea and Russia to push spam mail through my server. So I'm looking at tightening up the ipchains configuration to stop them. As Plusnet email comes in from a range of servers I'd either need to put them all in as separate addresses (which is a admin nightmare) or I'd need to put them in as a subnet or IP address range.
Has anyone else done this and if so which way did they do it?
thanks
Steve

[#2]

Well, if im correct in assuming you have your account set to smtp delivery to static ip, then you wont be able to.
What smtp forward does is to create an mx record, with a priorty of 1 so that all mailservers will connect directly to your static ip for delivery.
I wouldnt worry too much about the attempts, as long as they are being blocked.
Scott