run sieve on maildir

There's not an easy way to do this, but according to this message you can write a shell script to re-deliver messages using Dovecot's deliver program...so something like this:

produce_message_list |
while read msg; do
  /usr/libexec/dovecot/deliver -d user < $msg && rm -f $msg
done

You'll have to replace produce_message_list with something that produces a list of messages for processing; possibly find will do what you need.

Newer versions of dovecot and pidgeonhole now come with a sieve-filter command. So you can write a script to scan all mailboxes for a "INBOX.Refilter" folder, and then run sieve-filter against that folder.

This script assumes that you have structured your mail folder as /var/vmail/domain/user.

#!/bin/bash

FIND=/usr/bin/find
GREP=/bin/grep
RM=/bin/rm
SED=/bin/sed
SORT=/bin/sort

# BASE should point at /var/vmail/ and should have trailing slash
BASE="/var/vmail/"

RESORTFOLDER="INBOX.Refilter"

SEARCHFILE="dovecot-uidlist"

echo ""
echo "Search for messages to resort under ${BASE}"
echo "Started at: " `date`
echo "Looking for mailboxes with ${RESORTFOLDER}"
echo ""

# since RHEL5/CentOS5 don't have "sort -R" option to randomize, use the following example
# echo -e "2\n1\n3\n5\n4" | perl -MList::Util -e 'print List::Util::shuffle <>'

DIRS=`$FIND ${BASE} -maxdepth 3 -name ${SEARCHFILE} | \
    $SED -n "s:^${BASE}::p" | $SED "s:/${SEARCHFILE}$:/:" | \
    perl -MList::Util -e 'print List::Util::shuffle <>'`

# keep track of directories processed so far
DCNT=0

for DIR in ${DIRS}
do
    UD="${BASE}${DIR}.${RESORTFOLDER}"
    D=`echo "$DIR" | tr '/' ' ' | awk '{print $1}'`
    U=`echo "$DIR" | tr '/' ' ' | awk '{print $2}'`

    if [ -d "$UD/cur" ] 
    then
        echo "`date` - $DIR"
        echo " domain: $D"
        echo "   user: $U"
        FILES=`find $UD/cur/ $UD/new/ -type f -name '*' | wc -l`
        echo "  files: $FILES"

        if [[ $FILES -ge 1 ]]; then
            echo "Run $FILES messages back through the sieve filter."
            # -c2 means run at best-effort, -n7 is least priority possible
            ionice -c2 -n7 sieve-filter -e -W -C -u "${U}@${D}" "${BASE}${DIR}.dovecot.sieve" "${RESORTFOLDER}"
        fi

        echo ""
    fi

    # the following is debug code, to stop the script after N directories
    #DCNT=$(($DCNT+1))
    #echo "DCNT: $DCNT"
    #if [[ $DCNT -ge 5 ]]; then exit 0; fi
done

echo ""
echo "Finished at:" `date`
echo ""

I have searched a lot too - rarely documentated.

Meanwhile there is a command

sieve-filter

for it, found on this blog https://mebsd.com/configure-freebsd-servers/dovecot-pigeonhole-sieve-filter-refilter-delivered-email.html for a howto