Viewing File: /usr/local/cpanel/etc/exim/acls/ACL_CHECK_MESSAGE_PRE_BLOCK/default_check_message_pre

#
#  Enabling this will make the server non-rfc compliant
#  require verify = header_sender
#

    accept  hosts = : +loopback : +recent_authed_mail_ips : +backupmx_hosts

    accept
            authenticated = *
            hosts = *

    accept
            condition = %CPANEL-trustedmailhosts-size%
            hosts = +trustedmailhosts

    accept
            condition = %CPANEL-trustedmailhosts-size%
            condition = ${if match_ip{$sender_host_address}{net-iplsearch;/etc/trustedmailhosts}{1}{0}}