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What could possibly explain this weird behavior of email delivery?

Someone sent me an email message on February 16. I didn't received it neither immediately nor in the next days.

Then, out of the blue, EXACTLY 1 MONTH LATER (on March 16), I receive the message that he told me he sent on February 16.

I have seen bounced emails, I have seen lost emails, but I have never seen emails that get delivered exactly 1 month later.

Assuming that that guy indeed clicked the 'Send' button on February 16, what could possibly explain delivering it on March 16?

To help solve this mystery, I am quoting the header below (identifying details changed to protect privacy):

From - Wed Mar 16 14:55:21 2011
X-Account-Key: account3
X-UIDL: UID1720-1259701283
X-Mozilla-Status: 0003
X-Mozilla-Status2: 00000000
Return-path: <>
Delivery-date: Wed, 16 Mar 2011 13:18:14 -0500
Received: from ([]:52866)
    by with smtp (Exim 4.69)
    (envelope-from <>)
    id 1Q0H08-0004ke-5M
    for; Wed, 16 Mar 2011 13:18:14 -0500
Received: (qmail 9698 invoked from network); 16 Mar 2011 17:28:43 -0000
Received: from unknown (
  by ( with ESMTP; 16 Mar 2011 17:28:42 -0000
From: "Alan Doe" <>
To: "My Co" <>
Subject: Confidentiality Agreement
Date: Wed, 16 Mar 2011 13:18:10 -0400
Message-ID: <000001c7e4c8$c23e93f0$489bcbd0$>
MIME-Version: 1.0
Content-Type: multipart/alternative;
X-Mailer: Microsoft Outlook 14.0
Thread-Index: AbvPQ9BP9rTIPgVpRWqahWXuOLXz9g==
Content-Language: en-us
X-Spam-Status: No, score=0.3
X-Spam-Score: 3
X-Spam-Bar: /
X-Spam-Flag: NO

This is a multipart message in MIME format.

Content-Type: text/plain;
Content-Transfer-Encoding: 7bit
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Look at the Received: headers, starting at the last one and working up. The last one is:

Received: from unknown (
  by ( with ESMTP; 16 Mar 2011 17:28:42 -0000 is a Comcast customer:

$ nslookup
Non-authoritative answer:    name =

Since that's the first Received: header, it tells us that the message wasn't handed to a server until March 16. Note also the Date: header is March 16.

Thus the only conclusion I can come up with is the message sat in the sender's outbox for a month due to some misconfiguration or problem on the client end. Maybe his outgoing server configuration was wrong? Then whatever was wrong, it got fixed on March 16 and the mail client was able to successfully send the mail.

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My first suspicion would be an incorrect date setting on one of the systems involved. Send date is set by the system that creates the email, so if it has the wrong time it will be sent at the wrong time.

If he really did press send at that date it might have gotten stuck in the outbound e-mail queue of his mail client and then, by chance delivered a month later when he happened to restart the mail client or something similar.

It is unlikely to have been stuck at a mail server, as most mail servers will discard messages they can't deliver within a certain time frame (typically 4 days)

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