Restrict Postfix relay Front-end and Back-end postfix

[rafita69]

Hi all,

My question is a little bit complicated to write it.
I have as I said in the subject, a Front-end postfix and Back-end Post-fix.
The Front-End is analizing spam and virus with spamassassin and amavis. And then relay to the Back-end to deliver to mailboxes or relaying to Back-end to make it the back-end relay to the others servers.

Lately I got a huge queue 'cos I am getting mails as it was a open relay from one address to another where any of those address are from my domain. So everything goes slowly. I have set up to permit only networks I want ( I update the network_table with the addresses I want to allow to send mails.

I am getting connection from IP's that are not in mynetwork or in my network_table. Do you know why?
I am , as well, trying to test if it is behaving as a open relay and it is not `cos I tried with some webs and doing Telnet.
If the IP is not in network_table i got "Relay Access denied". If I write donw the IP, I got OK even if the e-mails are invented.

My question is:
1. Could I avoid this kind of behaviour? I mean, I want to check if the sender or recipient are from my domain ( or I am sending or I am gona receive=

2. Could I change the behabiour of my Front-End to allow to send message to my Back-end if it is for one of my addresses of my domain and if it is from my domain, to send directly to the server has to be send?