Ну на тебе, разрыв шаблона. Виртуалка на DO без ptr, в helo не fqdn запись
# host 104.236.152.242
Host 242.152.236.104.in-addr.arpa. not found: 3(NXDOMAIN)
Отправляем тестовое письмо
# echo "Hello world" | swaks -s 127.0.0.1 --from alex@mail.ru --to alex_hha@mail.ru --h-Subject "MAIL.RU relay test" --body -
=== Trying 127.0.0.1:25...
=== Connected to 127.0.0.1.
<- 220 centos-512mb-sfo1-01.localdomain ESMTP Postfix
-> EHLO centos-512mb-sfo1-01
<- 250-centos-512mb-sfo1-01.localdomain
<- 250-PIPELINING
<- 250-SIZE 10240000
<- 250-VRFY
<- 250-ETRN
<- 250-ENHANCEDSTATUSCODES
<- 250-8BITMIME
<- 250 DSN
-> MAIL FROM:<alex@mail.ru>
<- 250 2.1.0 Ok
-> RCPT TO:<alex_hha@mail.ru>
<- 250 2.1.5 Ok
-> DATA
<- 354 End data with <CR><LF>.<CR><LF>
-> Date: Thu, 04 Feb 2016 04:09:02 -0500
-> To: alex_hha@mail.ru
-> From: alex@mail.ru
-> Subject: MAIL.RU relay test
-> X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
->
-> Hello world
->
->
-> .
<- 250 2.0.0 Ok: queued as B8173403BF
-> QUIT
<- 221 2.0.0 Bye
=== Connection closed with remote host.
Смотрим логи локального mta
# cat /var/log/maillog | grep B8173403BF
Feb 4 04:09:02 centos-512mb-sfo1-01 postfix/smtpd[2078]: B8173403BF: client=localhost[127.0.0.1]
Feb 4 04:09:02 centos-512mb-sfo1-01 postfix/cleanup[2081]: B8173403BF: message-id=<20160204090902.B8173403BF@centos-512mb-sfo1-01.localdomain>
Feb 4 04:09:02 centos-512mb-sfo1-01 postfix/qmgr[1210]: B8173403BF: from=<alex@mail.ru>, size=459, nrcpt=1 (queue active)
Feb 4 04:09:05 centos-512mb-sfo1-01 postfix/smtp[2082]: B8173403BF: to=<alex_hha@mail.ru>, relay=mxs.mail.ru[94.100.180.150]:25, delay=2.3, delays=0.03/0/0.65/1.6, dsn=2.0.0, status=sent (250 OK id=1aRFuT-0006Y5-5A)
Feb 4 04:09:05 centos-512mb-sfo1-01 postfix/qmgr[1210]: B8173403BF: removed
Смотрим полученное мыло
Delivered-To: alex_hha@mail.ru
Return-path: <>
Authentication-Results: mxs.mail.ru; spf=softfail (mx96.mail.ru: transitioning domain of mail.ru does not designate 104.236.152.242 as permitted sender) smtp.mailfrom=alex@mail.ru smtp.helo=centos-512mb-sfo1-01.localdomain
Received-SPF: softfail (mx96.mail.ru: transitioning domain of mail.ru does not designate 104.236.152.242 as permitted sender) client-ip=104.236.152.242; envelope-from=alex@mail.ru; helo=centos-512mb-sfo1-01.localdomain;
Received: from [104.236.152.242] (port=36938 helo=centos-512mb-sfo1-01.localdomain)
by mx96.mail.ru with esmtp (envelope-from <alex@mail.ru>)
id 1aRFuT-0006Y5-5A
for alex_hha@mail.ru; Thu, 04 Feb 2016 12:09:05 +0300
X-Mru-BL: 0:0
X-Mru-BadRcptsCount: 0
X-Mru-PTR: error
X-Mru-NR: 1
X-Mru-OF: Linux (Ethernet or modem)
X-Mru-RC: unknown
Received: from centos-512mb-sfo1-01 (localhost [127.0.0.1])
by centos-512mb-sfo1-01.localdomain (Postfix) with ESMTP id B8173403BF
for <alex_hha@mail.ru>; Thu, 4 Feb 2016 04:09:02 -0500 (EST)
Date: Thu, 04 Feb 2016 04:09:02 -0500
To: alex_hha@mail.ru
From: alex@mail.ru
Subject: MAIL.RU relay test
X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
Message-Id: <20160204090902.B8173403BF@centos-512mb-sfo1-01.localdomain>
X-DMARC-Policy: none
X-DMARC-Result: fail
X-Mras: Ok
X-Mru-Authenticated-Sender: alex@mail.ru
X-Spam: undefined
Только не говори больше, что это криво настроен mail.ru/gmail.com :D
