disable SMTP auth required

Greetings all..... After spending days to find out how to setup my cPanel DNSONLY server [WHM 11.48.1 (build 3)] to act as a relay server for my selected clients, without having to create an email account locally on the server, solely an relay SMTP server, as there are some ISP's that have issues with their SMTP server, so I am offering this as a service to my clients only.....So I am trying to setup my SMTP server to either: [Legend:] whitelisted senders (/etc/exim/whitelist_sender <= has the clients EMAIL addresses listed in it) (a) disable it's authentication requirement and allow relays only for whitelisted senders, or (b) allow whitelisted_senders to relay emails without authentication, and if not whitelisted, then needs to authenticate before sending... ie. Client sends email || SMTP server || || |------> Email address Whitelisted? || ||-----NO | | | | | User Authenticated itself? | | | | | |--NO ==> REJECT | | |------Yes ====> Receive and relay (Send) email Above is ideally what I want to have.... Now many have commented the need to modify the section : "require verify = sender", but in this version of cpanel there is none... I have attached the exim.conf file for your review... Your assistance in this will be most appreciated.