Below URL receiving to recipient while sending emails to:
From: MAILER-DAEMON@yahoo.comSubject: Failure NoticeDate: 19 July 2013 19:09:48 BSTTo: Sorry, we were unable to deliver your message to the following address.:Remote host said: 530 5.7.1 Authentication required [MAIL_FROM]


Above error properly received to recipient end while sending emails to the server email address, few things need to verify.
1. Verify if client using Both MX record (external & local)
# root@server# host -t mx mail is handled by 0 mail is handled by 5

2. In above situation emails are routed (send-receive) from external host first then route to local server.
3. check the few files for correction. The domain entry correct on all below 3 files.
# /etc/locadomain
# /etc/remotedomain
# /etc/secondarymx
4. Restart exim and csf…!!

Fixed šŸ™‚