The /etc/sysconfig/exim file allows messages to be sent to one or more clients, routing the messages over whatever networks are necessary. The file sets the default values for exim to run. Its default values are set to run as a background daemon and to check its queue each hour in case something has backed up.
The values include:
DAEMON=, where <value><value>
yes — exim should be configured to listen to port 25 for incoming mail. yes implies the use of the Exim's -bd options.
no — exim should not be configured to listen to port 25 for incoming mail.
QUEUE=1h which is given to exim as -q$QUEUE. The -q option is not given to exim if /etc/sysconfig/exim exists and QUEUE is empty or undefined.