[Exim] Relay control problem - any ideas ?

Hi, guys --

I need to allow a Class C network to relay through an Exim 3.35 server,
*except* for one host.

I've tried a few ideas after reading the spec on exim.org, but I'm having
problems achieving this. To summarise :

A - exim.conf edit to show :
host_accept_relay = 127.0.0.1 : 192.168.100.0/24 : !192.168.100.1/32
Still permits relaying.

B - exim.conf edit to show :
host_accept_relay = 127.0.0.1 : 192.168.100.0/24
host_auth_accept_relay = 192.168.100.1/32
Still permits relay without authentication (my hope was that all hosts but one
would be able to relay without authentication, but attempts to relay through
that one host would fail since no authentication configuration exists.)

C - sender_net_reject
Not implimented in 3.35.


Anyone able to help me ? Ideally, it'd be handy for something similar to
attempt A to work, which said "let this network through, except this host".

Thanks for any help can be offered.



--
Regards, Andy Davidson
Systems Administrator
Comodo Research Labs