Почему не приходит почта?

Здравствуйте! Почему-то не приходит почта на сервер. Стоит связка Postfix + Dovecot + MySQL backend.
В логах почтового сервера, который должен принять почту, вижу это:

Feb  2 16:42:39 server postfix/smtpd[29994]: disconnect from forward5m.cmail.yandex.net[5.255.216.23] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
Feb  2 16:42:39 server postfix/virtual[29999]: warning: recipient user1@sub.domain.ru: not found in virtual_uid_maps
Feb  2 16:42:39 server postfix/virtual[29999]: 89BE7C49FD: to=<user1@sub.domain.ru>, relay=virtual, delay=0.06, delays=0.03/0.01/0/0.01, dsn=4.3.5, status=deferred (mail system configuration error)
Feb  2 16:45:31 server postfix/qmgr[29240]: A6C78C49F5: from=<dart@domain.ru>, size=76780, nrcpt=1 (queue active)
Feb  2 16:45:31 server postfix/virtual[30040]: warning: recipient user1@sub.domain.ru: not found in virtual_uid_maps
Feb  2 16:45:31 server postfix/virtual[30040]: A6C78C49F5: to=<user1@sub.domain.ru>, relay=virtual, delay=2388, delays=2388/0.02/0/0.01, dsn=4.3.5, status=deferred (mail system configuration error)
Feb  2 16:45:59 server postfix/anvil[29996]: statistics: max connection rate 1/60s for (smtp:5.255.216.23) at Feb  2 16:42:39
Feb  2 16:45:59 server postfix/anvil[29996]: statistics: max connection count 1 for (smtp:5.255.216.23) at Feb  2 16:42:39
Feb  2 16:45:59 server postfix/anvil[29996]: statistics: max cache size 1 at Feb  2 16:42:39
Feb  2 16:50:31 server postfix/qmgr[29240]: 89BE7C49FD: from=<dart@domain.ru>, size=77443, nrcpt=1 (queue active)
Feb  2 16:50:31 server postfix/virtual[30143]: warning: recipient user1@sub.domain.ru: not found in virtual_uid_maps
Feb  2 16:50:31 server postfix/virtual[30143]: 89BE7C49FD: to=<user1@sub.domain.ru>, relay=virtual, delay=472, delays=472/0.02/0/0.04, dsn=4.3.5, status=deferred (mail system configuration error)
Feb  2 16:50:38 server postfix/smtpd[30145]: connect from forward8o.cmail.yandex.net[37.9.109.55]
Feb  2 16:50:38 server postfix/smtpd[30145]: E7F09C49FF: client=forward8o.cmail.yandex.net[37.9.109.55]

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/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.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.

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = domain.ru
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = $myhostname,  localhost.domain.ru , localhost
relayhost = 
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
# директория для хранения почты
virtual_mailbox_base = /var/mail/
virtual_mailbox_domains = proxy:mysql:/etc/postfix/sql/mysql-virtual_domains.cf
virtual_alias_maps =   proxy:mysql:/etc/postfix/sql/mysql-virtual_forwardings.cf,  mysql:/etc/postfix/sql/mysql-virtual_email2email.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/sql/mysql-virtual_mailboxes.cf
local_recipient_maps = $virtual_mailbox_maps
relay_domains =

mysql-virtual_domains.cf :

user = mail
password = pass
dbname = mail
query = SELECT domain  FROM domains WHERE domain = '%s'
hosts = 127.0.0.1

mysql-virtual_mailboxes.cf :

user = mail
password = pass
dbname = mail
query = SELECT CONCAT( SUBSTRING_INDEX(email, '@', -1), '/' , SUBSTRING_INDEX(email, '@', 1), '/' ) FROM users WHERE email = '%s'
hosts = 127.0.0.1

mysql-virtual_forwardings.cf

user = mail
password = pass
dbname = mail
query = SELECT destination FROM forwardings WHERE source = '%s'
hosts = 127.0.0.1

mysql-virtual_email2email.cf :

user = mail
password = pass
dbname = mail
query = SELECT destination FROM forwardings WHERE source = '%s'
hosts = 127.0.0.1

В чём может быть причина?