formail
is a filter that can be used to format mail into mailbox format.

lockfile
is a utility that can lock a file for single use interactively or in a script.

mailstat
prints a summary report of mail that has been filtered by procmail since the last time mailstat was ran.

procmail
is an autonomous mail processor. It performs all the functions of an MDA (Mail Delivery Agent).

参考文献

• BLFS/Procmail-3.22