postfix + configuration Dovecot, pas de mails reçus

J'essaie d'installer un serveur de messagerie postfix + Dovecot sur mon propre serveur et j'ai des difficultés à recevoir du courrier. J'ai suivi ce tutoriel https://samhobbs.co.uk/2013/12/raspberry-pi-email-server-part-1-postfix (ainsi que quelques autres). Lorsque j'utilise Thunderbird, je peux me connecter à mon serveur et envoyer des messages. Mais les mails entrants ne sont pas reçus.

Voici à quoi ressemble mon fichier postfix main.cf :

# See /usr/share/postfix/main.cf.dist for a commented, more complete version

# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# TLS parameters
smtpd_tls_cert_file = /etc/ssl/certs/server.crt
smtpd_tls_key_file = /etc/ssl/private/server.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.

myhostname = embe-it.de
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = embe-it.de, h2535210.stratoserver.net, localhost.stratoserver.net, , localhost
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all

home_mailbox = Maildir/
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes 
smtpd_sasl_security_options = noanonymous
broken_sasl_auth_clients = yes

#smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
#smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination
#smtpd_client_restrictions = permit_networks, permit_sasl_authenticated, reject_unknown_client_hostname
#smtp_tls_security_level = may
#smtpd_tls_security_level = may
smtp_tls_note_starttls_offer = yes
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_auth_only = yes

Et voici le master.cf (pour activer les smtps) :

#
# Postfix master process configuration file.  For details on the format
# of the file, see the master(5) manual page (command: "man 5 master" or
# on-line: http://www.postfix.org/master.5.html).
#
# Do not forget to execute "postfix reload" after editing this file.
#
# ==========================================================================
# service type  private unpriv  chroot  wakeup  maxproc command + args
#               (yes)   (yes)   (yes)   (never) (100)
# ==========================================================================
smtp      inet  n       -       -       -       -       smtpd
#smtp      inet  n       -       -       -       1       postscreen
#smtpd     pass  -       -       -       -       -       smtpd
#dnsblog   unix  -       -       -       -       0       dnsblog
#tlsproxy  unix  -       -       -       -       0       tlsproxy
submission inet n       -       -       -       -       smtpd
  -o syslog_name=postfix/submission
  -o smtpd_tls_security_level=encrypt
  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
smtps     inet  n       -       -       -       -       smtpd
  -o syslog_name=postfix/smtps
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
# ...

Pour Dovecot j'ai édité 10-master.conf :

# ...
service imap-login {
  inet_listener imap {
    port = 143
  }
  inet_listener imaps {
    port = 993
    ssl = yes
  }

  # Number of connections to handle before starting a new process. Typically
  # the only useful values are 0 (unlimited) or 1. 1 is more secure, but 0
  # is faster. <doc/wiki/LoginProcess.txt>
  #service_count = 1

  # Number of processes to always keep waiting for more connections.
  #process_min_avail = 0

  # If you set service_count=0, you probably need to grow this.
  #vsz_limit = $default_vsz_limit
}
# ...

10-auth.conf :

# ...
disable_plaintext_auth = no
auth_mechanisms = plain login
# ...

Enfin, j'ai activé ssl dans 10-ssl.conf (en utilisant le certificat par défaut) :

# ...
ssl = required
# ...

Mon domaine est embe-it.de sur Ubuntu 14.04. J'ai créé un utilisateur appelé marvin et le Maildir, qui contient maintenant des fichiers créés par Dovecot ainsi que trois répertoires cur, new et tmp. Le journal montrait les courriers sortants, mais aucune erreur pour les courriers entrants (et maintenant, après l'avoir supprimé et recréé un fichier vide, il n'est plus peuplé). J'ai testé la connexion en utilisant telnet (à la fois localement et à distance), ce qui a fonctionné.

Avez-vous des suggestions ?