The regular Virtualmin default config should be like :
LOGFILE=/var/log/procmail.log
TRAP=/etc/webmin/virtual-server/procmail-logger.pl
:0wi
VIRTUALMIN=|/etc/webmin/virtual-server/lookup-domain.pl --exitcode 73 $LOGNAME
EXITCODE=$?
:0
* ?/bin/test "$EXITCODE" = "73"
/dev/null
EXITCODE=0
:0
* ?/bin/test "$VIRTUALMIN" != ""
{
INCLUDERC=/etc/webmin/virtual-server/procmail/$VIRTUALMIN
}
ORGMAIL=$HOME/Maildir/
DEFAULT=$HOME/Maildir/
DROPPRIVS=yes
:0
$DEFAULT