[Juser] Exodus + proxy

[primail]

Hello users !
I have some problems with Exodus ... i wont be able to sleep if  i cant 
solve them !
here is my network config :
Debian linux with the internet connection,
Win XP behind.
i have installed iptables a squid on debian
well exodus works very well, but i want to try the proxy option so i 
activate the proxy, etc
then, my exodus client can connect to the server, and squid shows one or 
two lines of logs toward exodus.jabberstudio.org
but it seams that the exodus client doesnt use Squid to connect because 
if i add this rule in my iptables :
iptables -I FORWARD -i eth+ -o ppp0 -p tcp --dport 5222 -j DROP , exodus 
doesnt work any more.
why ?

maybe i didnt understand the meaning of an http proxy in exodus ?

thanks a lot !!
best regards
christophe