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Full-Text Search


Full-text search allows all messages to be indexed, so that mail clients can quickly and efficiently search messages by their full text content. Dovecot supports a variety of community supported FTS indexing backends.

docker-mailserver comes pre-installed with two plugins that can be enabled with a dovecot config file.

Please be aware that indexing consumes memory and takes up additional disk space.


The dovecot-fts-xapian plugin makes use of Xapian. Xapian enables embedding an FTS engine without the need for additional backends.

The indexes will be stored as a subfolder named xapian-indexes inside your local mail-data folder (/var/mail internally). With the default settings, 10GB of email data may generate around 4GB of indexed data.

While indexing is memory intensive, you can configure the plugin to limit the amount of memory consumed by the index workers. With Xapian being small and fast, this plugin is a good choice for low memory environments (2GB) as compared to Solr.


  1. To configure fts-xapian as a dovecot plugin, create a file at docker-data/dms/config/dovecot/fts-xapian-plugin.conf and place the following in it:

    mail_plugins = $mail_plugins fts fts_xapian
    plugin {
        fts = xapian
        fts_xapian = partial=3 full=20 verbose=0
        fts_autoindex = yes
        fts_enforced = yes
        # disable indexing of folders
        # fts_autoindex_exclude = \Trash
        # Index attachements
        # fts_decoder = decode2text
    service indexer-worker {
        # limit size of indexer-worker RAM usage, ex: 512MB, 1GB, 2GB
        vsz_limit = 1GB
    # service decode2text {
    #     executable = script /usr/libexec/dovecot/
    #     user = dovecot
    #     unix_listener decode2text {
    #         mode = 0666
    #     }
    # }

    adjust the settings to tune for your desired memory limits, exclude folders and enable searching text inside of attachments

  2. Update docker-compose.yml to load the previously created dovecot plugin config file:

      version: '3.8'
          container_name: mailserver
          hostname: mail
          env_file: mailserver.env
            - "25:25"    # SMTP  (explicit TLS => STARTTLS)
            - "143:143"  # IMAP4 (explicit TLS => STARTTLS)
            - "465:465"  # ESMTP (implicit TLS)
            - "587:587"  # ESMTP (explicit TLS => STARTTLS)
            - "993:993"  # IMAP4 (implicit TLS)
            - ./docker-data/dms/mail-data/:/var/mail/
            - ./docker-data/dms/mail-state/:/var/mail-state/
            - ./docker-data/dms/mail-logs/:/var/log/mail/
            - ./docker-data/dms/config/:/tmp/docker-mailserver/
            - ./docker-data/dms/config/dovecot/fts-xapian-plugin.conf:/etc/dovecot/conf.d/10-plugin.conf:ro
            - /etc/localtime:/etc/localtime:ro
          restart: always
          stop_grace_period: 1m
            - NET_ADMIN
  3. Recreate containers:

    docker-compose down
    docker-compose up -d
  4. Initialize indexing on all users for all mail:

    docker-compose exec mailserver doveadm index -A -q \*
  5. Run the following command in a daily cron job:

    docker-compose exec mailserver doveadm fts optimize -A
    Or like the Spamassassin example shows, you can instead use cron from within docker-mailserver to avoid potential errors if the mail-server is not running:


Create a system cron file:

# in the docker-compose.yml root directory
mkdir -p ./docker-data/dms/cron # if you didn't have this folder before
touch ./docker-data/dms/cron/fts_xapian
chown root:root ./docker-data/dms/cron/fts_xapian
chmod 0644 ./docker-data/dms/cron/fts_xapian

Edit the system cron file nano ./docker-data/dms/cron/fts_xapian, and set an appropriate configuration:

# Adding `MAILTO=""` prevents cron emailing notifications of the task outcome each run
# m h dom mon dow user command
# Everyday 4:00AM, optimize index files
0  4 * * * root  doveadm fts optimize -A

Then with docker-compose.yml:

      - ./docker-data/dms/cron/fts_xapian:/etc/cron.d/fts_xapian


The dovecot-solr Plugin is used in conjunction with Apache Solr running in a separate container. This is quite straightforward to setup using the following instructions.

Solr is a mature and fast indexing backend that runs on the JVM. The indexes are relatively compact compared to the size of your total email.

However, Solr also requires a fair bit of RAM. While Solr is highly tuneable, it may require a bit of testing to get it right.


  1. docker-compose.yml:

        image: lmmdock/dovecot-solr:latest
          - ./docker-data/dms/config/dovecot/solr-dovecot:/opt/solr/server/solr/dovecot
        restart: always
          - solr
          - ./docker-data/dms/config/dovecot/10-plugin.conf:/etc/dovecot/conf.d/10-plugin.conf:ro
  2. ./docker-data/dms/config/dovecot/10-plugin.conf:

    mail_plugins = $mail_plugins fts fts_solr
    plugin {
      fts = solr
      fts_autoindex = yes
      fts_solr = url=http://solr:8983/solr/dovecot/
  3. Recreate containers: docker-compose down ; docker-compose up -d

  4. Flag all user mailbox FTS indexes as invalid, so they are rescanned on demand when they are next searched: docker-compose exec mailserver doveadm fts rescan -A

Further Discussion

See #905