cPanel v11 email: [mailconfigupdate] Unable to automaticlly update the mailer config on "hostname"

If you receive the following email on cPanel v11 and you’re running our MailScanner package or are not using the cPanel inbuilt SpamAssassin setup:

cPanel was unable to automatically merge your Exim configuration with the new settings that shipped with the build you have installed (cpanel_version) because you have a custom ACL configuration which cannot be automatically configured.