[exim] Question about Alias File Format

In my system alias file (declared by system_aliases in configuration file),
is there a simple way to simply reject an email address, even though it is a
valid email address on the server?

I want to stop the stuff coming to users like bin, sys, etc. It seems that
spammers are targeting these system accounts. I remember reading something
about putting the word "REJECT" on the line, but all of my searches of the
documentation and the list have come back empty.

I REALLY would rather create a list of email addresses to only accept email
from the server itself, but none from outside hosts. Has anyone done this
yet? I know I should be able to do this with a simple router, but am not
"that" good at creating routers yet.

Thanks in advance for your help


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