The postfix package contains bounce , cleanup, error, flush, lmtp, local, mailq, master, newaliases, nqmgr, pickup, pipe, postalias, postcat, postconf, postdrop, postfix, postkick, postlock, postlog, postmap, postqueue, postsuper, qmgr, qmqpd, sendmail, showq, smtp, smtpd, spawn, trivial-rewrite, and virtual. postfix is the program that starts and stops the mail delivery system. master is the resident process that runs bounce, cleanup, error, flush, lmtp, local, nqmgr, pickup, pipe, qmgr, qmqpd, showq, smtp, smtpd, spawn, trivial-rewrite and virtual on demand. These programs are not designed to work as user commands. postqueue implements the Postfix user interface for queue management. It implements all the operations that are traditionally available via the sendmail command. sendmail implements the Postfix to Sendmail compatibility interface. mailq and newaliases are symlinks to sendmail. showq will emulate the mailq command when the Postfix mail system is not running. postsuper does maintenance jobs on the Postfix queue. postalias creates, queries or updates Postfix alias databases. postcat prints the contents of a Postfix queue file in human-readable form. postconf prints or changes the value of configuration parameters. postdrop creates a file in the maildrop directory and copies its standard input to the file. postkick makes the mail system private IPC accessible for use in shell scripts. postlock locks a file for exclusive access and executes a command on that file. postlog implements a logging interface for use in shell scripts. postmap creates, queries or updates Postfix lookup tables.