For sendmail to process incoming mail, a daemon must be running. The sendmail daemon is the sendmail program with specific flags. (Appendix E describes the sendmail command-line flags in detail.) The daemon is automatically started by the /etc/init.d/mail script at station startup. The default command for the sendmail daemon is
/usr/lib/sendmail -bd -q15m
The -bd flag causes sendmail to run in daemon mode. The -q15m flag causes sendmail to fork a subdaemon for queue processing every fifteen minutes. The -bd and -q flags can be combined in one call.