Почему dovecot не доставляет электронные письма?

У меня проблема, что dovecot не доставляет электронные письма в мой почтовый ящик (roundcube).

мой dovecot.conf

base_dir = /var/run/dovecot
# Ich habe nur IMAP(S) in Verwendung, für POP3 einfach noch pop3 bzw. pop3s hinzufügen
protocols = imap imaps managesieve
# IMAP Konfiguration
protocol imap {
   listen = *:143
   # Quota Einstellungen
   mail_plugins = quota imap_quota
}

# einkommentieren, falls POP3 benötigt
#protocol pop3 {
#   listen = *:110
#   # ssl_listen = *:995
#   mail_plugins = quota
#}

# managesieve Dienst zum Verwalten der Sieve-Skripte
protocol managesieve {
   listen = *:2000
   login_executable = /usr/lib/dovecot/managesieve-login
   mail_executable = /usr/lib/dovecot/managesieve
   managesieve_max_line_length = 65536
   managesieve_logout_format = bytes=%i/%o
   managesieve_implementation_string = dovecot
}
listen = *
# erzwinge AUTH mit STARTTLS
disable_plaintext_auth = yes

# logging Optionen
log_path = /var/log/dovecot.log
info_log_path = /var/log/dovecot.log
log_timestamp = "%Y-%m-%d %H:%M:%S "
syslog_facility = mail

# mailbox Einstellungen
mail_location = maildir:/var/vmail/%d/%u
#mail_location = maildir:/var/spool/mail/%u
mail_privileged_group = mail
mail_debug = no

# gültig ist nur unser vmail-Besitzer
first_valid_uid = 150
last_valid_uid = 150

maildir_copy_with_hardlinks = yes

# IMAP Optionen
protocol imap {
  login_executable = /usr/lib/dovecot/imap-login
  mail_executable = /usr/lib/dovecot/imap
  imap_max_line_length = 65536
  mail_plugin_dir = /usr/lib/dovecot/modules/imap
}

#protocol pop3 {
#  pop3_uidl_format = %08Xu%08Xv
#}

# managesieve aktivieren
protocol managesieve {
}

# deliver aktivieren
protocol lda {
  postmaster_address = postmaster@lars-dev.de
  mail_plugins = quota sieve
  mail_plugin_dir = /usr/lib/dovecot/modules/lda
  deliver_log_format = msgid=%m: %$
  sendmail_path = /usr/lib/sendmail
  auth_socket_path = /var/run/dovecot/auth-master
}

auth_verbose = no
auth_debug = no

# Authentifizierungs-Info aus Datenbank
auth default {
  mechanisms = plain login

  passdb sql {
    args = /etc/dovecot/dovecot-sql.conf
  }

  # steigert Performance mit Datenbank
  userdb prefetch {
  }

  userdb sql {
    args = /etc/dovecot/dovecot-sql.conf
  }

  user = nobody

  socket listen {
    master {
      path = /var/run/dovecot/auth-master
      mode = 0660

      user = postfix
      group = mail
    }
    client {
      path = /var/spool/postfix/private/auth
      mode = 0660
      user = postfix
      group = postfix
    }
  }
}

# Quota-Info wird in Datenbank gespeichert
dict {
  quotadict = mysql:/etc/dovecot/dovecot-dict-sql.conf
  mail_debug = yes
}

# Quota & Sieve Konfiguration
plugin {
  quota = dict:user::proxy::quotadict
  quota_rule = *:storage=500MB
  sieve=~/dovecot.sieve
  sieve_dir=~/sieve
}

# SSL/TLS Konfig
ssl = yes
ssl_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
ssl_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
ssl_cipher_list = ALL:!LOW:!SSLv2
verbose_ssl = yes

mail.log

May 23 08:17:17 evolutio postfix/smtpd[21372]: connect from mout.gmx.net[212.227.17.20]
May 23 08:17:17 evolutio postfix/smtpd[21372]: A138C6020038: client=mout.gmx.net[212.227.17.20]
May 23 08:17:17 evolutio postfix/cleanup[21376]: A138C6020038: message-id=<trinity-b504aea3-1a03-4aa1-8326-4c352fc77086-1369289842779@3capp-gmx-bs54>
May 23 08:17:17 evolutio postfix/qmgr[1130]: A138C6020038: from=<evolutio1994@gmx.de>, size=1301, nrcpt=1 (queue active)
May 23 08:17:17 evolutio postfix/smtpd[21372]: disconnect from mout.gmx.net[212.227.17.20]
May 23 08:17:17 evolutio postfix/local[21377]: A138C6020038: to=<evolutio@lars-dev.de>, relay=local, delay=0.27, delays=0.17/0.01/0/0.09, dsn=2.0.0, status=sent (delivered to mailbox)
May 23 08:17:17 evolutio postfix/qmgr[1130]: A138C6020038: removed