Rebase Dovecot on Stretch slim, build from stable source with latest stable Pigeonhole for antispam replacement

docker-compose.yml

@@ -26,6 +26,7 @@ services:
       volumes:
         - mysql-vol-1:/var/lib/mysql/
         - ./data/conf/mysql/:/etc/mysql/conf.d/:ro
+        - ./data/assets/reset_mysql.sh:/reset_mysql.sh
       dns:
         - 172.22.1.254
       dns_search: mailcow-network
@@ -151,14 +152,16 @@ services:
       depends_on:
         - bind9-mailcow
       volumes:
-        - ./data/conf/dovecot:/etc/dovecot
+        - ./data/conf/dovecot:/usr/local/etc/dovecot
         - ./data/assets/ssl:/etc/ssl/mail/:ro
         - ./data/conf/sogo/:/etc/sogo/
         - vmail-vol-1:/var/vmail
+        - crypt-vol-1:/mail_crypt/
       environment:
         - DBNAME=${DBNAME}
         - DBUSER=${DBUSER}
         - DBPASS=${DBPASS}
+        - MAIL_CRYPT=${MAIL_CRYPT:-NO}
       ports:
         - "${IMAP_PORT:-143}:143"
         - "${IMAPS_PORT:-993}:993"
@@ -266,3 +269,4 @@ volumes:
   redis-vol-1:
   rspamd-vol-1:
   postfix-vol-1:
+  crypt-vol-1: