How to Read Bounceback Messages
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How to Read Bounceback Messages


Article ID: 179086


Updated On:






"Bounce" messages are a type of automatic responses sent by a program or server in reply to an email that has been received. 

Please note that there are many types of auto replies used in SMTP conversation and a bounce message is a type of auto reply. 

These messages are sent in accordance with RFC guidelines which require Mail Transfer Agents (MTAs) to inform the originator once it has accepted an email for relaying or forwarding purposes. 

Additional Information



In SMTP, bounce messages are sent using a null sender address: <>.  They also typically include a From: Mailer-Daemon on the recipient side. 

The main purpose of bounce messages are to enable administrators to spot problems and give enough information to facilitate a fix. 

Parts of a Bounce Message

Bounce messages usually contain information that assists the original sender in determining why the message was not delivered.

The common elements are outlined below. 

  • The date and time the message was bounced:

Last-Attempt-Date: Thu, 22 Jun 2017 14:12:36 -0700 (PDT)


  • The identity of the mail server that bounced it:


  • The reason that it was bounced (e.g. user unknown or Rejected by policy)

Diagnostic-Code: smtp; 553-Sorry, your email address [email protected] has
 553-been blacklisted.


  • The headers of the bounced message:

Delivered-To: [email protected]
Received: by with SMTP id q10csp620690oia;
        Thu, 22 Jun 2017 14:12:36 -0700 (PDT)
X-Received: by with SMTP id s35mr2637334ots.112.1498165956767;
        Thu, 22 Jun 2017 14:12:36 -0700 (PDT)


  • Some or all of the content of the bounced message: 

---------- Forwarded message ----------
From: Email Testers <[email protected]>
To: [email protected]
Date: Thu, 22 Jun 2017 17:12:34 -0400
Subject: Lorem Ipsum 2