Email error 550: 550 not permitted to relay through this server without authentication.

Hello

Yesterday I have faced an issue while trying to send mail to other mail account for eg, test@example.com.
2015-01-08 17:34:33 H=mail-qc0-f193.google.com [x.x.x.x]:34198 X=TLSv1:RC4-SHA:128 F=<test@gmail.com> rejected RCPT <test@example.com>: Please turn on SMTP Authentication in your mail client.  mail-qc0-f193.google.com [x.x.x.x]:34198 is not permitted to relay through this server without authentication.
I got this error while trying send mail from our test mail account to other mail account
Solution:
Check the text file /etc/localdomains and check to make sure the domains having problems are present in the list. If not, then add them to the list save the file and then Restart Exim for the changes to take effect. When an email is sent out from a cPanel server, exim checks /etc/localdomains and /etc/remotedomains in order to send the email to the correct place. If the domain is in /etc/localdomains, the mail is routed locally to the machine. If the domain is in /etc/remotedomains, the email is routed out to the Internet. This is useful if the domain has some software installed that sends email notifications, such as a content management system like WordPress. This ensures that mail will get sent to the correct location
Please note that always check /etc/localdomains when having email problems.
That’s it