[exim] [NEWBIE]Stop Spammers - How - Confused

Hi.

It appears that spammers are routinely using my Exim driven box to send their
spam... My users are either on broadband (cable modem, DSL), or dial up
connections. Assuming I want to route messages from *.accept-domain1.com and
*.accept-domain2.com, which of these options will work (for long version of
background story see below):

relay_domains = *.accept-domain1.com : *.accept-domain2.com

or should I use this instead:

host_accept_relay = 127.0.0.1 : ::::1 : *.accept-domain1.com : *.accept-domain2.com
(the above should have been a single line.)

or perhaps only this work will work:

host_auth_accept_relay = *.accept-domain1.com : *.accept-domain2.com

Some combination of the above?

(I've read about setting up user authentication, and whereas that sounds
attractive, it looks too complicated to me for a quick fix - have to download
and install additional software, notifty users to reconfigure their email
clients, support heachaches). Maybe later tonight, but I want to stop the
spammers NOW! - I already added an rbl_domains entry, which I hope will fight
off some of them...)

Any help would be appreciated.

TIA,
Joseph

LONG VERSION OF BACKGROUND
It appears that spammers are routinely using my Exim driven box to send their
spam... they must feel just comfy using my all-too liberal routing policy.
(They've brought my box down to a crawl several times, not to mention the
annoyance that is being caused to the recipients of the spam.)

My users are either on broadband (cable modem, DSL), or dial up connections. I
have identified the hosts used to originate email that I DO want to route. I
want to exclude any email that originates on other hosts.
I've looked at all the literature I could get my hands on, but I must admit, I'm
thoroughly confused.


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