Предупреждение Postfix: SASL: не удалось подключиться к / var / spool / postfix / private / auth: нет такого файла или каталога

Я искал, но не нашел ответа, и у меня нет идей. Я просто не знаю достаточно о postfix и dovecot, чтобы разбирать конфиги или понимать, что может вызывать эту ошибку.

warning: SASL: Connect to /var/spool/postfix/private/auth failed: No such file or directory
fatal: no SASL authentication mechanisms

Я не могу подключиться к внешним клиентам (например, Thunderbird) для постфикса с помощью SASL. Я надеюсь, что это что-то очевидное, но я просто не вижу этого.

1. /var/spool/postfix/private/auth существуют. Принадлежит postfix. Dovecot настроен на использование постфикса в качестве пользователя

2. Dovecot работает и слушает:
   unix 2 [ ACC ] STREAM LISTENING 241906 12768/dovecot /var/spool/postfix/private/auth

3. postconf -n вывод:

   alias_database = hash:/etc/aliases
   alias_maps = hash:/etc/aliases
   append_dot_mydomain = no
   biff = no
   broken_sasl_auth_clients = yes
   compatibility_level = 2
   inet_interfaces = all
   inet_protocols = all
   local_recipient_maps = $virtual_mailbox_maps
   local_transport = virtual
   mailbox_size_limit = 0
   milter_default_action = accept
   milter_protocol = 2
   mydestination = $myhostname, my-server.my-server.com, my-server, localhost.localdomain, localhost
   myhostname = my-server
   mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
   myorigin = /etc/mailname
   non_smtpd_milters = inet:localhost:12301
   readme_directory = no
   recipient_delimiter = +
   relay_domains = $mydestination, proxy:pgsql:/etc/postfix/pgsql/relay_domains.cf
   relayhost =
   smtp_sasl_auth_enable = yes
   smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
   smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
   smtpd_milters = inet:localhost:12301
   smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
   smtpd_sasl_auth_enable = yes
   smtpd_sasl_authenticated_header = yes
   smtpd_sasl_path = /var/spool/postfix/private/auth
   smtpd_sasl_security_options = noanonymous
   smtpd_sasl_type = dovecot
   smtpd_tls_cert_file = /etc/letsencrypt/live/mail.my-server.com/fullchain.pem
   smtpd_tls_key_file = /etc/letsencrypt/live/mail.my-server.com/privkey.pem
   smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
   smtpd_use_tls = yes
   virtual_alias_maps = proxy:pgsql:/etc/postfix/sql/psql_virtual_alias_maps.cf, proxy:pgsql:/etc/postfix/sql/psql_virtual_alias_domain_maps.cf, proxy:pgsql:/etc/postfix/sql/psql_virtual_alias_domain_catchall_maps.cf
   virtual_gid_maps = static:113
   virtual_mailbox_base = /var/mail/vmail
   virtual_mailbox_domains = proxy:pgsql:/etc/postfix/sql/psql_virtual_domains_maps.cf
   virtual_mailbox_limit = 512000000
   virtual_mailbox_maps = proxy:pgsql:/etc/postfix/sql/psql_virtual_mailbox_maps.cf, proxy:pgsql:/etc/postfix/sql/psql_virtual_alias_domain_mailbox_maps.cf
   virtual_minimum_uid = 113
   virtual_transport = virtual
   virtual_uid_maps = static:113
   

4. dovecot -n вывод:

   # 2.2.33.2 (d6601f4ec): /etc/dovecot/dovecot.conf
   # Pigeonhole version 0.4.21 (92477967)
   # OS: Linux 4.15.0-66-generic x86_64 Ubuntu 18.04.3 LTS ext4
   auth_mechanisms = plain login
   first_valid_uid = 113
   log_path = /var/log/dovecot.log
   login_greeting = My Mail Server
   mail_location = maildir:/var/mail/vmail/%u/
   mail_max_userip_connections = 50
   mail_plugins = " zlib"
   mail_privileged_group = mail
   namespace inbox {
     inbox = yes
     location =
     mailbox Drafts {
       special_use = \Drafts
     }
     mailbox Junk {
       special_use = \Junk
     }
     mailbox Sent {
       special_use = \Sent
     }
     mailbox "Sent Messages" {
       special_use = \Sent
     }
     mailbox Spam {
       special_use = \Junk
     }
     mailbox Trash {
       special_use = \Trash
     }
     prefix =
     type = private
   }
   passdb {
     driver = pam
   }
   passdb {
     args = /etc/dovecot/dovecot-sql.conf
     driver = sql
   }
   plugin {
     zlib_save = gz
     zlib_save_level = 6
   }
   protocols = imap pop3
   service auth {
     group = postfix
     unix_listener /var/spool/postfix/private/auth {
       group = postfix
       mode = 0666
       user = postfix
     }
     unix_listener auth-userdb {
       group = postfix
       mode = 0666
       user = postfix
     }
     user = postfix
   }
   service imap-login {
     inet_listener imaps {
       port = 993
       ssl = yes
     }
   }
   service imap {
     executable = imap
   }
   ssl_cert = </etc/letsencrypt/live/mail.my-server.com/fullchain.pem
   ssl_client_ca_dir = /etc/ssl/certs
   ssl_key =  # hidden, use -P to show it
   userdb {
     driver = passwd
   }
   userdb {
     args = /etc/dovecot/dovecot-sql.conf
     driver = sql
   }
   protocol imap {
     mail_plugins = " zlib imap_zlib"
   }