How to View – Analyze Message Source in Mail Delivery Subsystem messages.

Last updated on November 11th, 2016

Whenever you receive an email from "Mail Delivery Subsystem" or "Mailer-Daemon" with a subject "Mail delivery failed: returning message to sender", that means that a message that you have sent, for some reason, cannot be delivered to the recipient(s) and the message is returned back to you (bounced). In fact the "Mail delivery failed" is a returning report, produced automatically from the Mail server (commonly at the recipient's site) and contains the reason(s) for the delivery failure.

view analyze message source

There are many reasons why an email may return to you (bounce). The most common reason is that the recipient's address in entered incorrectly (user unknown). Other reasons may be that the email address doesn't exist any more, the file size of the message is too big , the recipient's inbox is full (mailbox over quota), a server error, the rejection of the message due to a spam filter, etc.

To read the Mail Delivery Error Reporting message, just open the message and at the first lines you will see why your messages weren't delivered.

e.g. "This is an automatically generated Delivery Status Notification.
THIS IS A WARNING MESSAGE ONLY. YOU DO NOT NEED TO RESEND YOUR MESSAGE.Delivery to the following recipient failed permanently:

If you want to view a more complete analysis of the delivery report, you must view the full "Message Source" (aka "All Header(s)" or "Full Header(s)" or "Internet headers") of the "Mail Delivery Failed" message.

How to view and analyze the full Message Source in Mail Delivery Subsystem messages (Identify the reason for the delivery failure).

Step 1. View/Open Message Source.

Notice: Keep in mind that if you use a local email client program such as Outlook, Thunderbird, etc., you can view the full message source only if you use a POP account. IMAP accounts don't support the view of the full message source but only the "basic" Internet Headers.


Outlook 2010 or Outlook 2013:

1. To view the full message source, open the message in Microsoft Outlook.

2a. Go next to Move item in the ribbon and click Actions > Other Actions > View Source.


2b. Click at the File menu and select Properties and see the Internet Headers section.

view message source outlook


Outlook 2007 & Outlook 2003:

To view the message source in Outlook 2007 or Outlook 2003:

  1. Open the message in Microsoft Outlook.
  2. On the ribbon click the small icon next to Options.
  3. View the Internet Headers section.

view internet headers outlook



To view the message source in Thunderbird:

    1. Select the message you'd like to view its source.
    2. From the main menu select View > Message Source.

message source thunderbird



To view the message source in Google Mail:

    1. Open the message you'd like to view.
    2. Click the down arrow next to Reply image_thumb[4], at the top of the message pane.
    3. Select Show Original.

message source gmail




To view the full message source in Outlook Mail (Hotmail):

  1. Right-click the message you'd like to view its source and select View Message Source.



To view the message source in Yahoo Mail:

    1. Select the message you'd like to view its source.
    2. Click Actions dropdown menu and select View Full Header.


Step 2. Identify the Mail Delivery Failure reason from Message Source.

The Message Source of a Mail Delivery Report, typically contains the following information:

1. The IP Address of the server that bounces the message and the date – time the message was returned (bounced) back to you.

e.g "Received: by with SMTP id j186csp81133vkg; Wed, 28 Oct 2015"

2. The mail server name (MAILER DAEMON) that bounced the message:

e.g. "From: Mail Delivery Subsystem <>
To: <YourEmailAddress>".

3. The reason why the message has returned to you (bounced).

Example No1: "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:

Example No2: "Technical details of permanent failure:=20
Google tried to deliver your message, but it was rejected by the server for=
the recipient domain by [<Mail Server IP Address>].
The error that the other server returned was: 550 Administrative prohibition

4. The last section contains the original message that was bounced.

That's it! Let me know if this guide has helped you by leaving your comment about your experience. Please like and share this guide to help others.

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