sudo postmap /etc/postfix/sasl_passwd
sudo chgrp postfix sasl_passwd*
sudo chmod 0640 sasl_passwd*
sudo postmap -q [smtp.gmail.com]:587 sasl_passwd

#Gmail SMTP
relayhost=smtp.gmail.com:587
# Enable SASL authentication in the Postfix SMTP client.
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options=noanonymous
smtp_sasl_mechanism_filter=plain
# Enable Transport Layer Security (TLS), i.e. SSL.
smtp_use_tls=yes
smtp_tls_security_level=encrypt
tls_random_source=dev:/dev/urandom

From MAILER-DAEMON  Thu Feb  9 14:53:14 2017
X-Original-To: Admin@MacBook-Pro.local
Delivered-To: Admin@MacBook-Pro.local
Date: Thu,  9 Feb 2017 14:53:14 +0530 (IST)
From: MAILER-DAEMON@MacBook-Pro.local (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
To: Admin@MacBook-Pro.local
Auto-Submitted: auto-replied
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
        boundary="CD41810841CF.1486632194/MacBook-Pro.local"

This is a MIME-encapsulated message.

--CD41810841CF.1486632194/MacBook-Pro.local
Content-Description: Notification
Content-Type: text/plain; charset=us-ascii

This is the mail system at host MacBook-Pro.local.

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

<varungupta.masters@gmail.com>: host smtp.gmail.com[74.125.200.109] said:
    530-5.5.1 Authentication Required. Learn more at 530 5.5.1
    https://support.google.com/mail/?p=WantAuthError a25sm27067419pgd.26 -
    gsmtp (in reply to MAIL FROM command)

--CD41810841CF.1486632194/MacBook-Pro.local
Content-Description: Delivery report
Content-Type: message/delivery-status

Reporting-MTA: dns; MacBook-Pro.local
X-Postfix-Queue-ID: CD41810841CF
X-Postfix-Sender: rfc822; Admin@MacBook-Pro.local
Arrival-Date: Thu,  9 Feb 2017 14:53:11 +0530 (IST)

Final-Recipient: rfc822; varungupta.masters@gmail.com
Original-Recipient: rfc822;varungupta.masters@gmail.com
Action: failed
Status: 5.5.1
Remote-MTA: dns; smtp.gmail.com
Diagnostic-Code: smtp; 530-5.5.1 Authentication Required. Learn more at 530
    5.5.1  https://support.google.com/mail/?p=WantAuthError a25sm27067419pgd.26
    - gsmtp

--CD41810841CF.1486632194/MacBook-Pro.local
Content-Description: Undelivered Message
Content-Type: message/rfc822

Return-Path: <Admin@MacBook-Pro.local>
Received: by MacBook-Pro.local (Postfix, from userid 501)
        id CD41810841CF; Thu,  9 Feb 2017 14:53:11 +0530 (IST)
To: varungupta.masters@gmail.com
Subject: testing
Message-Id: <20170209092311.CD41810841CF@MacBook-Pro.local>
Date: Thu,  9 Feb 2017 14:53:11 +0530 (IST)
From: Admin@MacBook-Pro.local (Admin)

Thu Feb  9 14:53:11 IST 2017

--CD41810841CF.1486632194/MacBook-Pro.local--

acBook-Pro.local--