Mail delivery failed: returning message to sender

[Mail Delivery System]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  sales at spitwspots.com
    host aspmx.l.google.com [74.125.142.26]
    SMTP error from remote mail server after end of data:
    550-5.7.1 This message does not have authentication information or fails to pass
    550-5.7.1 authentication checks. To best protect our users from spam, the
    550-5.7.1 message has been blocked. Please visit
    550-5.7.1  https://support.google.com/mail/answer/81126#authentication for more
    550 5.7.1 information. a23si3019943pls.189 - gsmtp
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From: Matthewsar <pkg-multimedia-maintainers at lists.alioth.debian.org>
Subject: New Message From Your Website
Date: Fri, 28 Jun 2019 15:58:43 -0600
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