[root@595ac83d263a ~]# echo "" > /var/log/maillog
[root@595ac83d263a ~]# echo "" > /var/spool/mail/root
[root@595ac83d263a ~]# echo "Body" | mail -s "Title NO SPAM" "alfreditospowerspam@gmail.com"
[root@595ac83d263a ~]# sleep 3
[root@595ac83d263a ~]# cat /var/log/maillog

Jul 29 21:51:41 595ac83d263a postfix/pickup[6910]: 155C112B64: uid=0 from=<root>
Jul 29 21:51:41 595ac83d263a postfix/cleanup[11283]: 155C112B64: message-id=<20150729215141.155C112B64@localhost>
Jul 29 21:51:41 595ac83d263a postfix/qmgr[6911]: 155C112B64: from=<root@localhost.localdomain>, size=439, nrcpt=1 (queue active)
Jul 29 21:51:41 595ac83d263a postfix/smtp[11287]: connect to gmail-smtp-in.l.google.com[2a00:1450:400c:c05::1b]:25: Network is unreachable
Jul 29 21:51:42 595ac83d263a postfix/smtp[11287]: 155C112B64: to=<alfreditospowerspam@gmail.com>, relay=gmail-smtp-in.l.google.com[173.194.67.26]:25, delay=1.2, delays=0.14/0.01/0.38/0.69, dsn=5.7.1, status=bounced (host gmail-smtp-in.l.google.com[173.194.67.26] said: 550-5.7.1 [79.150.9.233      12] Our system has detected that this message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550 5.7.1  https://support.google.com/mail/answer/188131 for more information. cx3si29457394wib.115 - gsmtp (in reply to end of DATA command))
Jul 29 21:51:42 595ac83d263a postfix/cleanup[11283]: 4BAB612B66: message-id=<20150729215142.4BAB612B66@localhost>
Jul 29 21:51:42 595ac83d263a postfix/bounce[11289]: 155C112B64: sender non-delivery notification: 4BAB612B66
Jul 29 21:51:42 595ac83d263a postfix/qmgr[6911]: 4BAB612B66: from=<>, size=2910, nrcpt=1 (queue active)
Jul 29 21:51:42 595ac83d263a postfix/qmgr[6911]: 155C112B64: removed
Jul 29 21:51:42 595ac83d263a postfix/local[11291]: 4BAB612B66: to=<root@localhost.localdomain>, relay=local, delay=0.13, delays=0.06/0.01/0/0.05, dsn=2.0.0, status=sent (delivered to mailbox)
Jul 29 21:51:42 595ac83d263a postfix/qmgr[6911]: 4BAB612B66: removed
[root@595ac83d263a ~]# cat /var/spool/mail/root

From MAILER-DAEMON  Wed Jul 29 21:51:42 2015
Return-Path: <>
X-Original-To: root@localhost.localdomain
Delivered-To: root@localhost.localdomain
Received: by localhost (Postfix)
	id 4BAB612B66; Wed, 29 Jul 2015 21:51:42 +0000 (UTC)
Date: Wed, 29 Jul 2015 21:51:42 +0000 (UTC)
From: MAILER-DAEMON@localhost.localdomain (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
To: root@localhost.localdomain
Auto-Submitted: auto-replied
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
	boundary="155C112B64.1438206702/localhost"
Message-Id: <20150729215142.4BAB612B66@localhost>

This is a MIME-encapsulated message.

--155C112B64.1438206702/localhost
Content-Description: Notification
Content-Type: text/plain; charset=us-ascii

This is the mail system at host localhost.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<alfreditospowerspam@gmail.com>: host gmail-smtp-in.l.google.com[173.194.67.26]
    said: 550-5.7.1 [79.150.9.233      12] Our system has detected that this
    message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam
    sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550
    5.7.1  https://support.google.com/mail/answer/188131 for more information.
    cx3si29457394wib.115 - gsmtp (in reply to end of DATA command)

--155C112B64.1438206702/localhost
Content-Description: Delivery report
Content-Type: message/delivery-status

Reporting-MTA: dns; localhost
X-Postfix-Queue-ID: 155C112B64
X-Postfix-Sender: rfc822; root@localhost.localdomain
Arrival-Date: Wed, 29 Jul 2015 21:51:41 +0000 (UTC)

Final-Recipient: rfc822; alfreditospowerspam@gmail.com
Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [79.150.9.233      12] Our system has detected
    that this message is 550-5.7.1 likely unsolicited mail. To reduce the
    amount of spam sent to Gmail, 550-5.7.1 this message has been blocked.
    Please visit 550 5.7.1  https://support.google.com/mail/answer/188131 for
    more information. cx3si29457394wib.115 - gsmtp

--155C112B64.1438206702/localhost
Content-Description: Undelivered Message
Content-Type: message/rfc822

Return-Path: <root@localhost.localdomain>
Received: by localhost (Postfix, from userid 0)
	id 155C112B64; Wed, 29 Jul 2015 21:51:41 +0000 (UTC)
Date: Wed, 29 Jul 2015 21:51:40 +0000
To: alfreditospowerspam@gmail.com
Subject: Title NO SPAM
User-Agent: Heirloom mailx 12.4 7/29/08
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-Id: <20150729215141.155C112B64@localhost>
From: root@localhost.localdomain (root)

Body

--155C112B64.1438206702/localhost--

[root@595ac83d263a ~]# postconf -n
alias_database = hash:/etc/aliases,hash:/etc/aliases.codendi,hash:/etc/aliases.codendi,hash:/etc/aliases.codendi
alias_maps = hash:/etc/aliases,hash:/etc/aliases.codendi,hash:/etc/aliases.codendi,hash:/etc/aliases.codendi
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = all	<--- ¿¿ I CHANGE THIS BECAUSE I USE RANGE 192.168.1.xxx ??
If i not change it, i get some error.... from localhost to all
inet_protocols = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost
myhostname = localhost
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550