postfix/dovecot - [private/dovecot-lmtp]: No such file or directory

[soko.tica]

Hello list,

I am trying to send a mail message from root to a system user on the same
box. While postfix functions without dovecot properly, once dovecot is
installed, I get the message from logs as set in the subject line - that
postfix/lmpt cannot connect to [private/dovecot-lmtp]: No such file or
directory

Also, user's ~/.Maildir aren't created, although there is such instructions
in dovecot. Finally, doveconf -n says there is no ssl enabled, although I
explicitly set it in /conf.d/10-ssl.conf

Below are dmesg, postconf -n, doveconf -n and a snippet from
/var/log/mail.log

Please advise. Thanks in advance.

$dmesg
[    0.000000] Linux version 3.18.26-x1-64 (root at dev0001.support.domain.tld)
(gcc version 4.4.5 (Debian 4.4.5-8) ) #1 SMP Mon Feb 8 11:43:41 GMT 2016
[    0.740773] pps_core: LinuxPPS API ver. 1 registered
================
$ postconf -n

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
config_directory = /etc/postfix
default_transport = error
delay_warning_time = 4h
inet_interfaces = loopback-only
mailbox_size_limit = 0
mailbox_transport = lmtp:unix:private/dovecot-lmtp
mydestination = $myhostname localhost.$mydomain localhost $mydomain
myhostname = mail.domain.tld
mynetworks = [::ffff:127.0.0.0]/104 [::1]/128
myorigin = $myhostname
notify_classes = resource, software
readme_directory = no
recipient_delimiter = +
relay_domains = $mydestination
relay_transport = error
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_use_tls = yes
==========================

$ doveconf -n
# 2.2.13: /etc/dovecot/dovecot.conf
# OS: Linux 3.18.26-x1-64 x86_64 Debian 8.3
hostname = mail.domain.tld
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
lda_original_recipient_header = X-Original-To
mail_location = maildir:~/Maildir
maildir_very_dirty_syncs = yes
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 Trash {
    special_use = \Trash
  }
  prefix =
  separator = /
  type = private
}
passdb {
  driver = pam
}
passdb {
  driver = pam
}
plugin {
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
}
postmaster_address = postmaster at mail.domain.tld
protocols = lmtp
service lmtp {
  unix_listener lmtp {
    group = postfix
    mode = 0600
    user = postfix
  }
}
ssl = no
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.pem
userdb {
  driver = passwd
}
userdb {
  driver = passwd
}
protocol lmtp {
  mail_fsync = optimized
}
protocol lda {
  mail_fsync = optimized
}
==============
$ cat /var/log/mail.log
Feb 21 23:20:40 boxname dovecot: master: Dovecot v2.2.13 starting up for
lmtp (core dumps disabled)
Feb 21 23:22:28 boxname postfix/pickup[32138]: EA06822140: uid=0 from=<root>
Feb 21 23:22:28 boxname postfix/cleanup[32177]: EA06822140:
message-id=<20160221232228.EA06822140 at mail.domain.tld>
Feb 21 23:22:28 boxname postfix/qmgr[32139]: EA06822140:
from=<root at mail.domain.tld>, size=333, nrcpt=1 (queue active)
Feb 21 23:22:29 boxname postfix/lmtp[32180]: EA06822140:
to=<brn at mail.domain.tld>, orig_to=<brn>, relay=none, delay=0.06,
delays=0.02/0.01/0.04/0, dsn=4.4.1, status=deferred (connect to
mail.domain.tld[private/dovecot-lmtp]: No such file or directory)