Delayed receipt of messages to Inbox

[#1]

Can anyone shed any light on why messages appear in Inbox three days after they were sent?

How can I find out where the delay occurs?

[#2]

The message transfer times in the headers will give you the relevant history.

[#3]

Thanks David. I have looked at the header, but not sure what this is telling me. Header info below, with hopefully all personal info removed! Unless I am not understanding the info correctly, the message appears to have been sent by marksandspencer on the 25th, and received by Plusnet gateway on the 28th. I'm still none the wiser as to why there is a 3 day delay! Nor do I know why there is a spurious smiley in the middle!

Return-path: <bounce-134041_HTML-637492411-5762675-1392844-799@bounce.news.marksandspencer.com>
Envelope-to: xxx@xxx.plus.com
Delivery-date: Sun, 28 Aug 2016 10:16:30 +0100
Received: from [212.159.9.108] (helo=avasin16.plus.net)
    by inmx14.plus.net with esmtp (PlusNet MXCore v2.00) id 1bdwCb-00018O-TU
    for xxx@xxx.plus.com; Sun, 28 Aug 2016 10:16:29 +0100
Received: from mta.news.marksandspencer.com ([66.231.95.42])
    by avasin16.plus.net with Plusnet Cloudmark Gateway
    id cZGS1t0030urL3E01ZGUMR; Sun, 28 Aug 2016 10:16:29 +0100
X-CM-Score: 0.00
X-CNFS-Analysis: v=2.2 cv=YO3d8lOx c=1 sm=1 tr=0 b=1
    a=d8HINz+SxF60OnAHAc2RUw==:117 a=d8HINz+SxF60OnAHAc2RUw==:17
    a=7z1cN_iqozsA:10 a=r77TgQKjGQsHNAKrUKIA:9 a=GSvKEVg1AAAA:8
    a=6TbBZxKlDqr-BOsdMfIA:9 a=Yk8v2DvnuLDAi6h8:21 a=edaZ_-GhTfz26gun:21
    a=QEXdDO2ut3YA:10 a=SSmOFEACAAAA:8 a=jSU605wCclGSJl1fjzIA:9
    a=gcVa-_iBXwSgBY-v:21 a=B9E51I2hMTLXUYce:21 a=7BueMQOUqK5n6vVu:21
    a=_W_S_7VecoQA:10 a=frz4AuCg-hUA:10 a=URENBqh2lzYA:10 a=p403mkujtbAA:10
    a=qtWtWivHcFxvU1QqmdEK:22 a=zjWhRoSqWz9hl55Hdlzg:22 awl=host:15048
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; s=200608; d=news.marksandspencer.com;
    h=From:To:Subject:Date:List-Unsubscribe:MIME-Version:Message-ID:Content-Type; i=sparks@news.marksandspencer.com;
    bh=HkagrAJVM/PHGfKSa2oCphQYLfs=;
    b=phOfRx0HHcBf+SgElBPyQ6eNbZ28NHycUByhWGPgW2i+TddAxTb69oHoIPXHhC33x8W2PFbSQa+Y
    ucLJD50QDr5VF8zv6NY3yG0pO+N6i2bcWa+3Ej1ONV89zOlaM76mrehiD+mwYWkQJ55b4qN1W4vp
    JSNi3l0itWF+5Vsj8xw=
Received: by mta.news.marksandspencer.com id hoaluq163hsr for <xxx@xxx.plus.com>; Thu, 25 Aug 2016 11:06:32 -0600 (envelope-from <bounce-134041_HTML-637492411-5762675-1392844-799@bounce.news.marksandspencer.com>)
From: "M&S Sparks" <sparks@news.marksandspencer.com>
To: <xxx@xxx.plus.com>
Date: Thu, 25 Aug 2016 11:06:32 -0600
List-Unsubscribe: <mailto:leave-fcbe15737164007c1a4c342838-fe2a127372600d7f711571-fe8911777366027a70-fe9015737c660c7971-ff5613797c@leave.news.marksandspencer.com>
MIME-Version: 1.0
x-job: 1392844_5762675
Message-ID: <f5e9990d-e9ae-4e5f-be8c-e360e6865573@xtnvmta101.xt.local>
Content-Type: multipart/alternative;
    boundary="xAzwCoCEJmJd=_?:"
X-PN-Virus-Filtered: by PlusNet MXCore (v5.00)
X-PN-Spam-Filtered: by PlusNet MXCore (v5.00)
Subject: Your new offers are in + 20% off beauty!

[#4]

Your analysis is correct. There is a 3 day delay between the message being received by the M & S mail server and it being accepted at Plusnet. However at our customer level we can't tell whether the delay is due to a backlog on the M & S server or due to Plusnet refusing the message for 3 days.

I guess it's a "see if it happens next time" situation.

The smiley on the message isn't really there. The header text contains <colon>D which is a short code for that smiley. Some email programs and this forum software will change <colon>D to that smiley as here ..