A0511: The system filter runs as root in Exim 4, unless you set system_filter_user to specify otherwise. When you set up a delivery direct from a system filter (an autoreply is a special kind of “delivery”) the transport runs as the same user, unless it has a user setting of its own. Normally, deliveries are not allowed to run as root as a security precaution; this is implemented by the never_users option.
The easiest solution is to add this to your configuration:
system_filter_user = exim
The system filter then runs as exim instead of root. Alternatively, you can arrange for autoreplies from the system filter to use a special transport of their own, and set the user option on that transport.
