mailcow-dockerized/data/conf/postfix/config_templates/mysql_recipient_bcc_maps.cf.j2

user = {{ DBUSER }}
password = {{ DBPASS }}
hosts = unix:/var/run/mysqld/mysqld.sock
dbname = {{ DBNAME }}
query = SELECT bcc_dest FROM bcc_maps
  WHERE local_dest='%s'
    AND type='rcpt'
    AND active='1';