==== Required information ====
- iRedMail version: 0.5.1
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: CentOS 5.4
- Related log if you're reporting an issue:
====

I'm trying to set up what microsoft calls a "smarthost". Ive got a running, established iRedMail server, that is currently acting as a backup MX for this domain for which i would like to set up "smarthost" services. I know that i need to add the ip address of the exchange server to the "mynetworks" section of main.cf, and i know how to configure my exchange server to use it. I dont know the following;

1. How do i set up authentication on the iRedMail system ?
2. How do i make sure that when the iRedMail system sends the mail for the exchange system, it leaves the original sender intact ?

I appreciate all of your help and guidance sir