[exim] Exim configuration question - reject email addressed …

Hello.

I'm having trouble.

I am working on an existing exim config file that has been tweaked to no
end. My goal is to reject email addressed to non-existent users at SMTP
time using ACLs and return a "no such user" error to the originating
server. But I'm having trouble getting it to work. Can I get some tips
on how to get that to work? I can provide the config file if it would
help, but I don't want to post that to the list.

On a slightly different note, I would also like to watch for hosts doing
"dictionary attacks" on my mail server and start filtering their IP
addresses (temporarily) to stop the storm of crap I'm getting. Any
ideas on how to do that?

Thanks.

Jarom Hatch