Trouble sending mails from a cPanel – server and you end up checking /var/log/exim_mainlog and able to spot something like this ?
Date H=(xxxx-xxx-xxx-xx-xx-co.in) [xx.xx.xx.xx]:xxxxxF= temporarily rejected RCPT : require_files: error for /home/x.com/etc/x.com: Permission denied
This happens when the permission or ownership has been altered for the given mailbox.
Fix this issue by :
/scripts/mailperm 'account-name'