diff --git a/data/Dockerfiles/dovecot/Dockerfile b/data/Dockerfiles/dovecot/Dockerfile
index c33772db4b..ed5ce90a11 100644
--- a/data/Dockerfiles/dovecot/Dockerfile
+++ b/data/Dockerfiles/dovecot/Dockerfile
@@ -24,6 +24,7 @@ RUN addgroup -g 5000 vmail \
   envsubst \
   ca-certificates \
   curl \
+  coreutils \
   jq \
   lua \
   lua-cjson \
@@ -103,7 +104,7 @@ RUN addgroup -g 5000 vmail \
   dovecot-submissiond \
   dovecot-pigeonhole-plugin \
   dovecot-pop3d \
-  dovecot-fts-solr \
+  dovecot-fts-flatcurve \
   && arch=$(arch | sed s/aarch64/arm64/ | sed s/x86_64/amd64/) \
   && wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$arch" \
   && chmod +x /usr/local/bin/gosu \
@@ -127,6 +128,7 @@ COPY stop-supervisor.sh /usr/local/sbin/stop-supervisor.sh
 COPY quarantine_notify.py /usr/local/bin/quarantine_notify.py
 COPY quota_notify.py /usr/local/bin/quota_notify.py
 COPY repl_health.sh /usr/local/bin/repl_health.sh
+COPY optimize-fts.sh /usr/local/bin/optimize-fts.sh
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 CMD exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf
diff --git a/data/Dockerfiles/dovecot/docker-entrypoint.sh b/data/Dockerfiles/dovecot/docker-entrypoint.sh
index a9545f338b..1abb8dfc1d 100755
--- a/data/Dockerfiles/dovecot/docker-entrypoint.sh
+++ b/data/Dockerfiles/dovecot/docker-entrypoint.sh
@@ -109,14 +109,14 @@ EOF
 
 echo -n ${ACL_ANYONE} > /etc/dovecot/acl_anyone
 
-if [[ "${SKIP_SOLR}" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
+if [[ "${SKIP_FLATCURVE}" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
 echo -n 'quota acl zlib mail_crypt mail_crypt_acl mail_log notify listescape replication' > /etc/dovecot/mail_plugins
 echo -n 'quota imap_quota imap_acl acl zlib imap_zlib imap_sieve mail_crypt mail_crypt_acl notify listescape replication mail_log' > /etc/dovecot/mail_plugins_imap
 echo -n 'quota sieve acl zlib mail_crypt mail_crypt_acl notify listescape replication' > /etc/dovecot/mail_plugins_lmtp
 else
-echo -n 'quota acl zlib mail_crypt mail_crypt_acl mail_log notify fts fts_solr listescape replication' > /etc/dovecot/mail_plugins
-echo -n 'quota imap_quota imap_acl acl zlib imap_zlib imap_sieve mail_crypt mail_crypt_acl notify mail_log fts fts_solr listescape replication' > /etc/dovecot/mail_plugins_imap
-echo -n 'quota sieve acl zlib mail_crypt mail_crypt_acl fts fts_solr notify listescape replication' > /etc/dovecot/mail_plugins_lmtp
+echo -n 'quota acl zlib mail_crypt mail_crypt_acl mail_log notify fts fts_flatcurve listescape replication' > /etc/dovecot/mail_plugins
+echo -n 'quota imap_quota imap_acl acl zlib imap_zlib imap_sieve mail_crypt mail_crypt_acl notify mail_log fts fts_flatcurve listescape replication' > /etc/dovecot/mail_plugins_imap
+echo -n 'quota sieve acl zlib mail_crypt mail_crypt_acl fts fts_flatcurve notify listescape replication' > /etc/dovecot/mail_plugins_lmtp
 fi
 chmod 644 /etc/dovecot/mail_plugins /etc/dovecot/mail_plugins_imap /etc/dovecot/mail_plugins_lmtp /templates/quarantine.tpl
 
@@ -343,6 +343,10 @@ mail_replica = tcp:${MAILCOW_REPLICA_IP}:${DOVEADM_REPLICA_PORT}
 EOF
 fi
 
+if [[ "${SKIP_FLATCURVE}" =~ ^([nN][oO]|[nN])+$ ]]; then
+  sed -i "s/vsz_limit\s*=\s*[0-9]*\s*MB*/vsz_limit=${FTS_HEAP} MB/" /etc/dovecot/conf.d/fts-flatcurve.conf
+  sed -i "s/process_limit\s*=\s*[0-9]*/process_limit=${FTS_PROCS}/" /etc/dovecot/conf.d/fts-flatcurve.conf
+fi
 
 # 401 is user dovecot
 if [[ ! -s /mail_crypt/ecprivkey.pem || ! -s /mail_crypt/ecpubkey.pem ]]; then
@@ -387,7 +391,8 @@ chmod +x /usr/lib/dovecot/sieve/rspamd-pipe-ham \
   /usr/local/bin/maildir_gc.sh \
   /usr/local/sbin/stop-supervisor.sh \
   /usr/local/bin/quota_notify.py \
-  /usr/local/bin/repl_health.sh
+  /usr/local/bin/repl_health.sh \
+  /usr/local/bin/optimize-fts.sh
 
 # Prepare environment file for cronjobs
 printenv | sed 's/^\(.*\)$/export \1/g' > /source_env.sh
diff --git a/data/Dockerfiles/dovecot/optimize-fts.sh b/data/Dockerfiles/dovecot/optimize-fts.sh
new file mode 100644
index 0000000000..d9de7da3e3
--- /dev/null
+++ b/data/Dockerfiles/dovecot/optimize-fts.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [[ "${SKIP_FLATCURVE}" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
+    exit 0
+else
+    doveadm fts optimize -A
+fi
diff --git a/data/conf/dovecot/conf.d/fts-flatcurve.conf b/data/conf/dovecot/conf.d/fts-flatcurve.conf
new file mode 100644
index 0000000000..a9240f5519
--- /dev/null
+++ b/data/conf/dovecot/conf.d/fts-flatcurve.conf
@@ -0,0 +1,24 @@
+plugin {
+    fts_autoindex = yes
+    fts_autoindex_exclude = \Junk
+    fts_autoindex_exclude2 = \Trash
+    fts = flatcurve
+    
+    # These are not flatcurve settings, but required for Dovecot FTS. See
+    # Dovecot FTS Configuration link above for further information.
+    fts_languages = en es de
+    fts_tokenizer_generic = algorithm=simple
+    fts_tokenizers = generic email-address
+
+    # OPTIONAL: Recommended default FTS core configuration
+    fts_filters = normalizer-icu snowball stopwords
+    fts_filters_en = lowercase snowball english-possessive stopwords
+
+}
+
+service indexer-worker {
+  executable = /bin/nice -n 10 /usr/libexec/dovecot/indexer-worker
+  process_limit=5
+
+  vsz_limit=256 MB
+}
\ No newline at end of file
diff --git a/data/conf/dovecot/dovecot.conf b/data/conf/dovecot/dovecot.conf
index 729686fb18..f71f85c00a 100644
--- a/data/conf/dovecot/dovecot.conf
+++ b/data/conf/dovecot/dovecot.conf
@@ -10,6 +10,7 @@
 auth_mechanisms = plain login
 #mail_debug = yes
 #auth_debug = yes
+log_debug = category=fts-flatcurve
 log_path = syslog
 disable_plaintext_auth = yes
 # Uncomment on NFS share
@@ -194,9 +195,6 @@ plugin {
   acl_shared_dict = file:/var/vmail/shared-mailboxes.db
   acl = vfile
   acl_user = %u
-  fts = solr
-  fts_autoindex = yes
-  fts_solr = url=http://solr:8983/solr/dovecot-fts/
   quota = dict:Userquota::proxy::sqlquota
   quota_rule2 = Trash:storage=+100%%
   sieve = /var/vmail/sieve/%u.sieve
@@ -305,6 +303,7 @@ replication_dsync_parameters = -d -l 30 -U -n INBOX
 !include_try /etc/dovecot/extra.conf
 !include_try /etc/dovecot/sogo-sso.conf
 !include_try /etc/dovecot/shared_namespace.conf
+!include_try /etc/dovecot/conf.d/fts-flatcurve.conf
 # </Includes>
 default_client_limit = 10400
 default_vsz_limit = 1024 M
diff --git a/docker-compose.yml b/docker-compose.yml
index 1a0588877f..f3e9c3f128 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -158,7 +158,7 @@ services:
         - API_KEY_READ_ONLY=${API_KEY_READ_ONLY:-invalid}
         - API_ALLOW_FROM=${API_ALLOW_FROM:-invalid}
         - COMPOSE_PROJECT_NAME=${COMPOSE_PROJECT_NAME:-mailcow-dockerized}
-        - SKIP_SOLR=${SKIP_SOLR:-y}
+        - SKIP_FLATCURVE=${SKIP_FLATCURVE:-y}
         - SKIP_CLAMD=${SKIP_CLAMD:-n}
         - SKIP_SOGO=${SKIP_SOGO:-n}
         - ALLOW_ADMIN_EMAIL_LOGIN=${ALLOW_ADMIN_EMAIL_LOGIN:-n}
@@ -221,7 +221,7 @@ services:
             - sogo
 
     dovecot-mailcow:
-      image: mailcow/dovecot:1.29
+      image: mailcow/dovecot:dev
       depends_on:
         - mysql-mailcow
         - netfilter-mailcow
@@ -258,7 +258,9 @@ services:
         - ALLOW_ADMIN_EMAIL_LOGIN=${ALLOW_ADMIN_EMAIL_LOGIN:-n}
         - MAILDIR_GC_TIME=${MAILDIR_GC_TIME:-7200}
         - ACL_ANYONE=${ACL_ANYONE:-disallow}
-        - SKIP_SOLR=${SKIP_SOLR:-y}
+        - SKIP_FLATCURVE=${SKIP_FLATCURVE:-y}
+        - FTS_HEAP=${FTS_HEAP:-512}
+        - FTS_PROCS=${FTS_PROCS:-3}
         - MAILDIR_SUB=${MAILDIR_SUB:-}
         - MASTER=${MASTER:-y}
         - REDIS_SLAVEOF_IP=${REDIS_SLAVEOF_IP:-}
@@ -550,27 +552,6 @@ services:
           aliases:
             - dockerapi
 
-    
-    ##### Will be removed soon #####
-    solr-mailcow:
-      image: mailcow/solr:1.8.2
-      restart: always
-      depends_on:
-        - netfilter-mailcow
-      volumes:
-        - solr-vol-1:/opt/solr/server/solr/dovecot-fts/data
-      ports:
-        - "${SOLR_PORT:-127.0.0.1:18983}:8983"
-      environment:
-        - TZ=${TZ}
-        - SOLR_HEAP=${SOLR_HEAP:-1024}
-        - SKIP_SOLR=${SKIP_SOLR:-y}
-      networks:
-        mailcow-network:
-          aliases:
-            - solr
-    ################################
-
     olefy-mailcow:
       image: mailcow/olefy:1.13
       restart: always
@@ -626,7 +607,6 @@ services:
         - netfilter-mailcow
         - watchdog-mailcow
         - dockerapi-mailcow
-        - solr-mailcow
       environment:
         - TZ=${TZ}
       image: robbertkl/ipv6nat
@@ -658,7 +638,6 @@ volumes:
   mysql-socket-vol-1:
   redis-vol-1:
   rspamd-vol-1:
-  solr-vol-1:
   postfix-vol-1:
   crypt-vol-1:
   sogo-web-vol-1:
diff --git a/generate_config.sh b/generate_config.sh
index f97ddd9a4e..2441a9e3ea 100755
--- a/generate_config.sh
+++ b/generate_config.sh
@@ -163,26 +163,6 @@ else
   SKIP_CLAMD=n
 fi
 
-if [ ${MEM_TOTAL} -le "2097152" ]; then
-  echo "Disabling Solr on low-memory system."
-  SKIP_SOLR=y
-elif [ ${MEM_TOTAL} -le "3670016" ]; then
-  echo "Installed memory is <= 3.5 GiB. It is recommended to disable Solr to prevent out-of-memory situations."
-  echo "Solr is a prone to run OOM and should be monitored. The default Solr heap size is 1024 MiB and should be set in mailcow.conf according to your expected load."
-  echo "Solr can be re-enabled by setting SKIP_SOLR=n in mailcow.conf but will refuse to start with less than 2 GB total memory."
-  read -r -p  "Do you want to disable Solr now? [Y/n] " response
-  case $response in
-    [nN][oO]|[nN])
-      SKIP_SOLR=n
-      ;;
-    *)
-      SKIP_SOLR=y
-    ;;
-  esac
-else
-  SKIP_SOLR=n
-fi
-
 if [[ ${SKIP_BRANCH} != y ]]; then
   echo "Which branch of mailcow do you want to use?"
   echo ""
@@ -382,14 +362,21 @@ SKIP_CLAMD=${SKIP_CLAMD}
 
 SKIP_SOGO=n
 
-# Skip Solr on low-memory systems or if you do not want to store a readable index of your mails in solr-vol-1.
+# Skip Flatcurve (FTS) on low-memory systems or if you simply want to disable it.
+
+SKIP_FLATCURVE=n
+
+# Dovecot Indexing (FTS) Process maximum heap size in MB, there is no recommendation, please see Dovecot docs.
+# Flatcurve (Xapian backend) is used as the FTS Indexer. It is supposed to be efficient in CPU and RAM consumption.
+# However: Please always monitor your Resource consumption!
 
-SKIP_SOLR=${SKIP_SOLR}
+FTS_HEAP=512
 
-# Solr heap size in MB, there is no recommendation, please see Solr docs.
-# Solr is a prone to run OOM and should be monitored. Unmonitored Solr setups are not recommended.
+# Controls how many processes the Dovecot indexing process can spawn at max.
+# Too many indexing processes can use a lot of CPU and Disk I/O.
+# Please visit: https://doc.dovecot.org/configuration_manual/service_configuration/#indexer-worker for more informations
 
-SOLR_HEAP=1024
+FTS_PROCS=5
 
 # Allow admins to log into SOGo as email user (without any password)
 
diff --git a/update.sh b/update.sh
index 0c8f85fedc..338ed4a4cb 100755
--- a/update.sh
+++ b/update.sh
@@ -275,6 +275,405 @@ detect_bad_asn() {
   fi
 }
 
+adapt_new_options() {
+
+  CONFIG_ARRAY=(
+  "SKIP_LETS_ENCRYPT"
+  "SKIP_SOGO"
+  "USE_WATCHDOG"
+  "WATCHDOG_NOTIFY_EMAIL"
+  "WATCHDOG_NOTIFY_WEBHOOK"
+  "WATCHDOG_NOTIFY_WEBHOOK_BODY"
+  "WATCHDOG_NOTIFY_BAN"
+  "WATCHDOG_NOTIFY_START"
+  "WATCHDOG_EXTERNAL_CHECKS"
+  "WATCHDOG_SUBJECT"
+  "SKIP_CLAMD"
+  "SKIP_IP_CHECK"
+  "ADDITIONAL_SAN"
+  "DOVEADM_PORT"
+  "IPV4_NETWORK"
+  "IPV6_NETWORK"
+  "LOG_LINES"
+  "SNAT_TO_SOURCE"
+  "SNAT6_TO_SOURCE"
+  "COMPOSE_PROJECT_NAME"
+  "DOCKER_COMPOSE_VERSION"
+  "SQL_PORT"
+  "API_KEY"
+  "API_KEY_READ_ONLY"
+  "API_ALLOW_FROM"
+  "MAILDIR_GC_TIME"
+  "MAILDIR_SUB"
+  "ACL_ANYONE"
+  "FTS_HEAP"
+  "FTS_PROCS"
+  "SKIP_FLATCURVE"
+  "ENABLE_SSL_SNI"
+  "ALLOW_ADMIN_EMAIL_LOGIN"
+  "SKIP_HTTP_VERIFICATION"
+  "SOGO_EXPIRE_SESSION"
+  "REDIS_PORT"
+  "DOVECOT_MASTER_USER"
+  "DOVECOT_MASTER_PASS"
+  "MAILCOW_PASS_SCHEME"
+  "ADDITIONAL_SERVER_NAMES"
+  "ACME_CONTACT"
+  "WATCHDOG_VERBOSE"
+  "WEBAUTHN_ONLY_TRUSTED_VENDORS"
+  "SPAMHAUS_DQS_KEY"
+  "SKIP_UNBOUND_HEALTHCHECK"
+  "DISABLE_NETFILTER_ISOLATION_RULE"
+  )
+
+  sed -i --follow-symlinks '$a\' mailcow.conf
+  for option in ${CONFIG_ARRAY[@]}; do
+    if [[ ${option} == "ADDITIONAL_SAN" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "${option}=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "COMPOSE_PROJECT_NAME" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "COMPOSE_PROJECT_NAME=mailcowdockerized" >> mailcow.conf
+      fi
+    elif [[ ${option} == "DOCKER_COMPOSE_VERSION" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "# Used Docker Compose version" >> mailcow.conf
+        echo "# Switch here between native (compose plugin) and standalone" >> mailcow.conf
+        echo "# For more informations take a look at the mailcow docs regarding the configuration options." >> mailcow.conf
+        echo "# Normally this should be untouched but if you decided to use either of those you can switch it manually here." >> mailcow.conf
+        echo "# Please be aware that at least one of those variants should be installed on your maschine or mailcow will fail." >> mailcow.conf
+        echo "" >> mailcow.conf
+        echo "DOCKER_COMPOSE_VERSION=${DOCKER_COMPOSE_VERSION}" >> mailcow.conf
+      fi
+    elif [[ ${option} == "DOVEADM_PORT" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "DOVEADM_PORT=127.0.0.1:19991" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_NOTIFY_EMAIL" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "WATCHDOG_NOTIFY_EMAIL=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "LOG_LINES" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Max log lines per service to keep in Redis logs' >> mailcow.conf
+        echo "LOG_LINES=9999" >> mailcow.conf
+      fi
+    elif [[ ${option} == "IPV4_NETWORK" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Internal IPv4 /24 subnet, format n.n.n. (expands to n.n.n.0/24)' >> mailcow.conf
+        echo "IPV4_NETWORK=172.22.1" >> mailcow.conf
+      fi
+    elif [[ ${option} == "IPV6_NETWORK" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Internal IPv6 subnet in fc00::/7' >> mailcow.conf
+        echo "IPV6_NETWORK=fd4d:6169:6c63:6f77::/64" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SQL_PORT" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Bind SQL to 127.0.0.1 on port 13306' >> mailcow.conf
+        echo "SQL_PORT=127.0.0.1:13306" >> mailcow.conf
+      fi
+    elif [[ ${option} == "API_KEY" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Create or override API key for web UI' >> mailcow.conf
+        echo "#API_KEY=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "API_KEY_READ_ONLY" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Create or override read-only API key for web UI' >> mailcow.conf
+        echo "#API_KEY_READ_ONLY=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "API_ALLOW_FROM" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Must be set for API_KEY to be active' >> mailcow.conf
+        echo '# IPs only, no networks (networks can be set via UI)' >> mailcow.conf
+        echo "#API_ALLOW_FROM=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SNAT_TO_SOURCE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Use this IPv4 for outgoing connections (SNAT)' >> mailcow.conf
+        echo "#SNAT_TO_SOURCE=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SNAT6_TO_SOURCE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Use this IPv6 for outgoing connections (SNAT)' >> mailcow.conf
+        echo "#SNAT6_TO_SOURCE=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "MAILDIR_GC_TIME" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Garbage collector cleanup' >> mailcow.conf
+        echo '# Deleted domains and mailboxes are moved to /var/vmail/_garbage/timestamp_sanitizedstring' >> mailcow.conf
+        echo '# How long should objects remain in the garbage until they are being deleted? (value in minutes)' >> mailcow.conf
+        echo '# Check interval is hourly' >> mailcow.conf
+        echo 'MAILDIR_GC_TIME=1440' >> mailcow.conf
+      fi
+    elif [[ ${option} == "ACL_ANYONE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Set this to "allow" to enable the anyone pseudo user. Disabled by default.' >> mailcow.conf
+        echo '# When enabled, ACL can be created, that apply to "All authenticated users"' >> mailcow.conf
+        echo '# This should probably only be activated on mail hosts, that are used exclusivly by one organisation.' >> mailcow.conf
+        echo '# Otherwise a user might share data with too many other users.' >> mailcow.conf
+        echo 'ACL_ANYONE=disallow' >> mailcow.conf
+      fi
+    elif [[ ${option} == "FTS_HEAP" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Dovecot Indexing (FTS) Process maximum heap size in MB, there is no recommendation, please see Dovecot docs.' >> mailcow.conf
+        echo '# Flatcurve is used as FTS Engine. It is supposed to be pretty efficient in CPU and RAM consumption.' >> mailcow.conf
+        echo '# Please always monitor your Resource consumption!' >> mailcow.conf
+        echo "FTS_HEAP=1024" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SKIP_FLATCURVE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Skip Flatcurve (FTS) on low-memory systems or if you simply want to disable it.' >> mailcow.conf
+        echo "SKIP_FLATCURVE=y" >> mailcow.conf
+      fi
+    elif [[ ${option} == "FTS_PROCS" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Controls how many processes the Dovecot indexing process can spawn at max.' >> mailcow.conf
+        echo '# Too many indexing processes can use a lot of CPU and Disk I/O' >> mailcow.conf
+        echo '# Please visit: https://doc.dovecot.org/configuration_manual/service_configuration/#indexer-worker for more informations' >> mailcow.conf
+        echo "FTS_PROCS=5" >> mailcow.conf
+      fi
+    elif [[ ${option} == "ENABLE_SSL_SNI" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Create seperate certificates for all domains - y/n' >> mailcow.conf
+        echo '# this will allow adding more than 100 domains, but some email clients will not be able to connect with alternative hostnames' >> mailcow.conf
+        echo '# see https://wiki.dovecot.org/SSL/SNIClientSupport' >> mailcow.conf
+        echo "ENABLE_SSL_SNI=n" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SKIP_SOGO" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Skip SOGo: Will disable SOGo integration and therefore webmail, DAV protocols and ActiveSync support (experimental, unsupported, not fully implemented) - y/n' >> mailcow.conf
+        echo "SKIP_SOGO=n" >> mailcow.conf
+      fi
+    elif [[ ${option} == "MAILDIR_SUB" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# MAILDIR_SUB defines a path in a users virtual home to keep the maildir in. Leave empty for updated setups.' >> mailcow.conf
+        echo "#MAILDIR_SUB=Maildir" >> mailcow.conf
+        echo "MAILDIR_SUB=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_NOTIFY_WEBHOOK" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Send notifications to a webhook URL that receives a POST request with the content type "application/json".' >> mailcow.conf
+        echo '# You can use this to send notifications to services like Discord, Slack and others.' >> mailcow.conf
+        echo '#WATCHDOG_NOTIFY_WEBHOOK=https://discord.com/api/webhooks/XXXXXXXXXXXXXXXXXXX/XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_NOTIFY_WEBHOOK_BODY" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# JSON body included in the webhook POST request. Needs to be in single quotes.' >> mailcow.conf
+        echo '# Following variables are available: SUBJECT, BODY' >> mailcow.conf
+        WEBHOOK_BODY='{"username": "mailcow Watchdog", "content": "**${SUBJECT}**\n${BODY}"}'
+        echo "#WATCHDOG_NOTIFY_WEBHOOK_BODY='${WEBHOOK_BODY}'" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_NOTIFY_BAN" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Notify about banned IP. Includes whois lookup.' >> mailcow.conf
+        echo "WATCHDOG_NOTIFY_BAN=y" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_NOTIFY_START" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Send a notification when the watchdog is started.' >> mailcow.conf
+        echo "WATCHDOG_NOTIFY_START=y" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_SUBJECT" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Subject for watchdog mails. Defaults to "Watchdog ALERT" followed by the error message.' >> mailcow.conf
+        echo "#WATCHDOG_SUBJECT=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_EXTERNAL_CHECKS" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Checks if mailcow is an open relay. Requires a SAL. More checks will follow.' >> mailcow.conf
+        echo '# No data is collected. Opt-in and anonymous.' >> mailcow.conf
+        echo '# Will only work with unmodified mailcow setups.' >> mailcow.conf
+        echo "WATCHDOG_EXTERNAL_CHECKS=n" >> mailcow.conf
+      fi
+    elif [[ ${option} == "SOGO_EXPIRE_SESSION" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# SOGo session timeout in minutes' >> mailcow.conf
+        echo "SOGO_EXPIRE_SESSION=480" >> mailcow.conf
+      fi
+    elif [[ ${option} == "REDIS_PORT" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "REDIS_PORT=127.0.0.1:7654" >> mailcow.conf
+      fi
+    elif [[ ${option} == "DOVECOT_MASTER_USER" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# DOVECOT_MASTER_USER and _PASS must _both_ be provided. No special chars.' >> mailcow.conf
+        echo '# Empty by default to auto-generate master user and password on start.' >> mailcow.conf
+        echo '# User expands to DOVECOT_MASTER_USER@mailcow.local' >> mailcow.conf
+        echo '# LEAVE EMPTY IF UNSURE' >> mailcow.conf
+        echo "DOVECOT_MASTER_USER=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "DOVECOT_MASTER_PASS" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# LEAVE EMPTY IF UNSURE' >> mailcow.conf
+        echo "DOVECOT_MASTER_PASS=" >> mailcow.conf
+      fi
+    elif [[ ${option} == "MAILCOW_PASS_SCHEME" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Password hash algorithm' >> mailcow.conf
+        echo '# Only certain password hash algorithm are supported. For a fully list of supported schemes,' >> mailcow.conf
+        echo '# see https://docs.mailcow.email/models/model-passwd/' >> mailcow.conf
+        echo "MAILCOW_PASS_SCHEME=BLF-CRYPT" >> mailcow.conf
+      fi
+    elif [[ ${option} == "ADDITIONAL_SERVER_NAMES" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Additional server names for mailcow UI' >> mailcow.conf
+        echo '#' >> mailcow.conf
+        echo '# Specify alternative addresses for the mailcow UI to respond to' >> mailcow.conf
+        echo '# This is useful when you set mail.* as ADDITIONAL_SAN and want to make sure mail.maildomain.com will always point to the mailcow UI.' >> mailcow.conf
+        echo '# If the server name does not match a known site, Nginx decides by best-guess and may redirect users to the wrong web root.' >> mailcow.conf
+        echo '# You can understand this as server_name directive in Nginx.' >> mailcow.conf
+        echo '# Comma separated list without spaces! Example: ADDITIONAL_SERVER_NAMES=a.b.c,d.e.f' >> mailcow.conf
+        echo 'ADDITIONAL_SERVER_NAMES=' >> mailcow.conf
+      fi
+    elif [[ ${option} == "ACME_CONTACT" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Lets Encrypt registration contact information' >> mailcow.conf
+        echo '# Optional: Leave empty for none' >> mailcow.conf
+        echo '# This value is only used on first order!' >> mailcow.conf
+        echo '# Setting it at a later point will require the following steps:' >> mailcow.conf
+        echo '# https://docs.mailcow.email/troubleshooting/debug-reset_tls/' >> mailcow.conf
+        echo 'ACME_CONTACT=' >> mailcow.conf
+      fi
+    elif [[ ${option} == "WEBAUTHN_ONLY_TRUSTED_VENDORS" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "# WebAuthn device manufacturer verification" >> mailcow.conf
+        echo '# After setting WEBAUTHN_ONLY_TRUSTED_VENDORS=y only devices from trusted manufacturers are allowed' >> mailcow.conf
+        echo '# root certificates can be placed for validation under mailcow-dockerized/data/web/inc/lib/WebAuthn/rootCertificates' >> mailcow.conf
+        echo 'WEBAUTHN_ONLY_TRUSTED_VENDORS=n' >> mailcow.conf
+      fi
+    elif [[ ${option} == "SPAMHAUS_DQS_KEY" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo "# Spamhaus Data Query Service Key" >> mailcow.conf
+        echo '# Optional: Leave empty for none' >> mailcow.conf
+        echo '# Enter your key here if you are using a blocked ASN (OVH, AWS, Cloudflare e.g) for the unregistered Spamhaus Blocklist.' >> mailcow.conf
+        echo '# If empty, it will completely disable Spamhaus blocklists if it detects that you are running on a server using a blocked AS.' >> mailcow.conf
+        echo '# Otherwise it will work as usual.' >> mailcow.conf
+        echo 'SPAMHAUS_DQS_KEY=' >> mailcow.conf
+      fi
+    elif [[ ${option} == "WATCHDOG_VERBOSE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Enable watchdog verbose logging' >> mailcow.conf
+        echo 'WATCHDOG_VERBOSE=n' >> mailcow.conf
+      fi
+    elif [[ ${option} == "SKIP_UNBOUND_HEALTHCHECK" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Skip Unbound (DNS Resolver) Healthchecks (NOT Recommended!) - y/n' >> mailcow.conf
+        echo 'SKIP_UNBOUND_HEALTHCHECK=n' >> mailcow.conf
+      fi
+    elif [[ ${option} == "DISABLE_NETFILTER_ISOLATION_RULE" ]]; then
+      if ! grep -q ${option} mailcow.conf; then
+        echo "Adding new option \"${option}\" to mailcow.conf"
+        echo '# Prevent netfilter from setting an iptables/nftables rule to isolate the mailcow docker network - y/n' >> mailcow.conf
+        echo '# CAUTION: Disabling this may expose container ports to other neighbors on the same subnet, even if the ports are bound to localhost' >> mailcow.conf
+        echo 'DISABLE_NETFILTER_ISOLATION_RULE=n' >> mailcow.conf
+      fi 
+    elif ! grep -q ${option} mailcow.conf; then
+      echo "Adding new option \"${option}\" to mailcow.conf"
+      echo "${option}=n" >> mailcow.conf
+    fi
+  done
+}
+
+migrate_solr_config_options() {
+
+  SOLR_OPTIONS=(
+  "SOLR_HEAP"
+  "SOLR_PORT"
+  "SKIP_SOLR"
+  )
+
+  sed -i --follow-symlinks '$a\' mailcow.conf
+  for option in "${SOLR_OPTIONS[@]}"; do
+  if [[ $option == "SOLR_HEAP" ]]; then
+    if grep -q "${option}" mailcow.conf; then
+      echo "Replacing SOLR_HEAP with \"${option}\" in mailcow.conf"
+      sed -i '/# Solr heap size in MB\b/c\# Dovecot Indexing (FTS) Process heap size in MB, there is no recommendation, please see Dovecot docs.' mailcow.conf
+      sed -i '/# Solr is a prone to run\b/c\# Flatcurve is replacing solr as FTS Indexer completely. It is supposed to be much more efficient in CPU and RAM consumption.'  mailcow.conf
+      sed -i 's/SOLR_HEAP/FTS_HEAP/g' mailcow.conf
+    fi
+  fi
+  if [[ $option == "SKIP_SOLR" ]]; then
+    if grep -q "${option}" mailcow.conf; then
+      echo "Replacing $option in mailcow.conf with SKIP_FLATCURVE"
+      sed -i '/\bSkip Solr on low-memory\b/c\# Skip Flatcurve (FTS) on low-memory systems or if you simply want to disable it.' mailcow.conf
+      sed -i '/\bSolr is disabled by default\b/d' mailcow.conf
+      sed -i '/\bDisable Solr or\b/d' mailcow.conf
+      sed -i 's/SKIP_SOLR/SKIP_FLATCURVE/g' mailcow.conf
+    fi
+  fi
+  if [[ $option == "SOLR_PORT" ]]; then
+    if grep -q "${option}" mailcow.conf; then
+      echo "Removing ${option} in mailcow.conf"
+      sed -i '/\bSOLR_PORT\b/d' mailcow.conf
+    fi
+  fi
+  done
+
+  solr_volume=$(docker volume ls -qf name=^${COMPOSE_PROJECT_NAME}_solr-vol-1)
+  if [[ -n $solr_volume ]]; then
+    echo -e "\e[34mSolr has been replaced within mailcow since 2024-XX.\e[0m"
+    sleep 1
+    echo -e "\e[34mTherefore the volume $solr_volume is unused.\e[0m"
+    sleep 1
+    read -r -p "Would you like to remove the $solr_volume? " response
+    if [[ "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
+      echo -e "\e[33mRemoving $solr_volume...\e[0m"
+      docker volume rm $solr_volume
+      if [[ $? != 0 ]]; then
+        echo -e "\e[31mCould not remove the volume... Please remove it manually!\e[0m"
+      else
+        echo -e "\e[32mSucessfully removed $solr_volume!\e[0m"
+      fi
+    else
+      echo "Ok! Not removing $solr_volume then."
+      echo "Once you decided on removing the volume simply run docker volume rm $solr_volume to remove it manually."
+      echo "This can be done anytime. mailcow does not use this volume anymore."
+    fi
+  fi  
+}
+
 ############## End Function Section ##############
 
 # Check permissions
@@ -932,7 +1331,8 @@ for container in "${MAILCOW_CONTAINERS[@]}"; do
 done
 
 [[ -f data/conf/nginx/ZZZ-ejabberd.conf ]] && rm data/conf/nginx/ZZZ-ejabberd.conf
-
+migrate_solr_config_options
+adapt_new_options
 
 # Silently fixing remote url from andryyy to mailcow
 # git remote set-url origin https://github.com/mailcow/mailcow-dockerized