[root@mail ~]# cat /etc/postfix/main.cf
relayhost =
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/private/sasl_passwd

smtp_sasl_security_options = noanonymous
smtp_sasl_type = cyrus
smtp_sasl_mechanism_filter = login
smtp_sender_dependent_authentication = yes
sender_dependent_relayhost_maps = hash:/etc/postfix/private/sender_relay
sender_canonical_maps = hash:/etc/postfix/private/canonical

#smtp_tls_CAfile = /etc/postfix/ca_yandex.pem

#  reject domen bk.ru
smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/conf/sender_access, reject


[root@mail ~]# cat /etc/postfix/private/canonical
@yandex osslabs@yandex.ru
[root@mail ~]# cat /etc/postfix/private/sender_relay
@yandex.ru smtp.yandex.ru
[root@mail ~]# cat /etc/postfix/private/sasl_passwd
[smtp.yandex.ru] osslabs@yandex.ru:Password
[root@mail ~]# cat /etc/postfix/conf/sender_access
@gmail.com REJECT

[root@mail ~]echo «test-test-test» | mutt -s «Tema-test26» llikodhuk@gmail.com
Apr 20 01:04:31 mail postfix/pickup[4632]: CF4735E87: uid=0 from=<root>
Apr 20 01:04:31 mail postfix/cleanup[4642]: CF4735E87: message-id=<20180420050431.GA4638@mail.osslabs.ru>
Apr 20 01:04:31 mail postfix/qmgr[4633]: CF4735E87: from=<root@mail.osslabs.ru>, size=491, nrcpt=1 (queue active)
Apr 20 01:04:32 mail postfix/smtp[4644]: CF4735E87: to=<llikodhuk@gmail.com>, relay=gmail-smtp-in.l.google.com[209.85.233.27]:25, delay=0.87, delays=0.03/0/0.39/0.45, dsn=2.0.0, status=sent (250 2.0.0 OK 1524200672 z4si1943774ljj.309 - gsmtp)
Apr 20 01:04:32 mail postfix/qmgr[4633]: CF4735E87: removed

==============================================Приходит от рута  (так не нужно) ====== Да и запрет я ставил на отправку на gmail.com
«Tema-test26»
root <root@mail.osslabs.ru>
9:04 (4 мин. назад)
кому: мне
«test-test-test»