how to restrict senders by COS
I've been searching for a senders' restriction in order to prevent a big part of our users to send email to internet.
I've found a wiki document, but I wondered if there is a solution integrated to the last updated versions (the 5.0.9 version is the last version for today).
I'm looking at the wiki doc but it doesn't meet all my requirements : the documentation offers a way to restrict senders (so that external users can't send to our distribution lists or users), another documentation offers a way to restrict recipients (so that an user can't send to some recipients), but there is no information about making an automatic filter.
Let me explain : we have different COS, so, I simply need to configure my Postfix to make a search for the user in order to see if he/she can send to internet users.
But LDAP is an heavy protocol, so it implies to know the impact on the traffic performance ...
Did anyone set up an equivalent configuration ?
I take all informations available ! :D