Philip Guenther wrote in response to Elmar Bins,
| Delivery mode is invoked using the -d flag. All arguments are the -d
| are usernames. It is usually used by the MTA to deliver mail to users,
| and indeed, procmail will return failure if it is given an invalid
| username.
Procmail will work in delivery mode only if it is setuid root, if it is
invoked with the ruid of the recipient named in -d, or, under certain OSes
where the build routines have determined that it is safe, if the euid is
that of the recipient and the egid is the recipient's login group.
| Mailfilter mode is invoked using the -m flag. It accepts only one
| rcfile as an argument -- other arguments are either variable
| assignments or arguments that are made availible to the rcfile itself
| as $1, $2, etc.
Only one rcfile can be named on the command line, but names of other rcfiles
can be passed in the positional parameters to be used later in INCLUDERC
assignments.
| If the specified rcfile is located under
| /etc/procmailrc/ then procmail will take on the uid of the owner of
| that file.
That should be /etc/procmailrcs/. /etc/procmailrc is the rcfile that
procmail -d reads and should not be a directory.