The sendmail program is run by specifying its name followed by command-line switches, then recipient addresses. Some command-line switches cause sendmail to ignore its recipients, while others require their presence. One switch, -bt, places sendmail into interactive, rule-testing mode.
Prints persistent host status information (see §36.1.1).
Prints the queue's contents (see §36.1.2).
Rebuilds the aliases database file or files (see §36.1.3).
Purges (zeroes) persistent host status information (see §36.1.4).
Runs in daemon mode (see §36.1.5).