If you have cpanel license and can update it to the latest non-vulnerable patched version, then it is the easiest fix , else please do the below steps: Complete below modification and restart exim, also check mail service by sending test mail. Also make sure to take backup of exim.conf, before modification Open /etc/exim.conf, SEARCH FOR acl_not_smtp:* and add below content ############################### deny    condition = ${if lt {$exim_version}{4.92}{1}{0}}    condition = ${if forany{<,$recipients}{match_local_part{$item}{\N^.*\$\{.*$\N}}{yes}{no}}    message = restricted characters in recipient address deny    condition = ${if lt {$exim_version}{4.92}{1}{0}}    condition = ${if match{$sender_address_local_part}{\N^.*\$\{.*$\N}{yes}{no}}    message = restricted characters in sender address # END INSERT 000_restricted_chars # BEGIN INSERT resolve_vhost_owner warn        condition  = ${if eq{$originator_uid}{${perl{user2ui