Maildrop is available at http://www.courier-mta.org/maildrop 
Although it is the default LDA for the courier mail server, it also works as a standalone LDA.  The install script can even build an rpm package if you prefer to manage software that way.  Maildrop can be used with sendmail as a drop-in replacement for procmail.  It has better maildir support than procmail and it has filtering capability using syntax that looks a lot like shell script language with a little bit of perl thrown in. 
To use maildrop with sendmail, make the following change in your sendmail.mc file, then make etc. 

---%<-------------------------------------------------------------------------
dnl FEATURE(local_procmail,',procmail -t -Y -a $h -d $u')dnl
dnl # replace above line with below line to use maildrop instead of procmail
FEATURE(local_procmail', /usr/bin/maildrop', `maildrop -d $u')dnl
 ---%<-------------------------------------------------------------------------

A default system wide configuration file for maildir style mailboxes might look like the following: 

---%<-------------------------------------------------------------------------
# file: /etc/maildroprc
# system-wide settings for maildrop

SHELL="/bin/bash"
SENDMAIL="/usr/sbin/sendmail -oi -t"
logfile "/var/log/maildrop.log"

DEFAULT="$HOME/Maildir/"
---%<-------------------------------------------------------------------------

In the above configuration, the users should be a member of the same group and the group should have write privileges to the logfile. 
(This file was created from the wiki on 2007-12-11 04:42)
