Столкнулся с непонятным.
Создал "Домен". Завёл пользователей. Открыл порты. Пробую доставить почту - получаю ошибку:
Проверил - домен в /etc/postfix/mydestination имеется.
Пришлось в итоге добавлять все почтовые адреса в /etc/postfix/recipient_access.
Содержимое main.cf прилагаю.
Спойлер
# Global Postfix configuration file. This file lists only a small subset
# of all parameters. For the syntax, and for a complete parameter list,
# see the postconf(5) manual page. For a commented and more complete
# version of this file see /etc/postfix/main.cf.dist
mynetworks = localhost, $myhostname, $config_directory/mynetworks
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
broken_sasl_auth_clients = yes
smtpd_use_tls = yes
smtpd_tls_key_file = /var/lib/ssl/private/postfix.key
smtpd_tls_cert_file = /var/lib/ssl/certs/postfix.cert
smtpd_helo_required = yes
smtpd_helo_restrictions = check_recipient_access cdb:/etc/postfix/whitelist, permit_mynetworks, permit_sasl_authenticated, check_helo_access cdb:/etc/postfix/helo_access, reject_non_fqdn_hostname, reject_invalid_hostname, permit
smtpd_client_restrictions = check_recipient_access cdb:/etc/postfix/whitelist, permit_mynetworks, permit_sasl_authenticated, check_client_access cdb:/etc/postfix/client_access, reject_rbl_client xbl.spamhaus.org, reject_rbl_client zen.spamhaus.org, permit
smtpd_sender_restrictions = check_recipient_access cdb:/etc/postfix/whitelist, permit_mynetworks, permit_sasl_authenticated, check_sender_access cdb:/etc/postfix/sender_access, reject_non_fqdn_sender, reject_unknown_sender_domain, permit
smtpd_recipient_restrictions = check_recipient_access cdb:/etc/postfix/recipient_access, permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, reject
#virtual_alias_maps = ldap:/etc/postfix/ldap-aliases.cf, ldap:/etc/postfix/ldap-users.cf
#local_recipient_maps = proxy:unix:passwd.byname $alias_maps ldap:/etc/postfix/ldap-users.cf
local_recipient_maps = proxy:unix:passwd.byname $alias_maps
mailbox_unpriv_delivery = no
relayhost =
message_size_limit = 33554432
smtpd_sasl_security_options = noplaintext, noanonymous
smtpd_sasl_tls_security_options = noanonymous
content_filter = scan:127.0.0.1:10026
smtpd_tls_auth_only = yes
mailbox_size_limit = 2147483648
receive_override_options = no_address_mappings