Receiving duplicate emails - differing virus checks?

[#1]

I use fetchmail to make POP3 connections to my PlusNet mailbox, using uidl to determine which emails have already been 'seen' locally.
In the last week or so, my mailbox has suddenly filled with 'duplicate' emails. The uidl shows that the emails are new (e.g. the number of messages doubles). The message ids are the same, *but* the headers associated with spam and virus checking are different, for example:

Received: from mx.ironport.plus.net (HELO relay.ptn-ipout02.plus.net) ([84.92.2.97])  by mx.ptn-ipin04.plus.net with ESMTP; 09 Jun 2010 13:56:47 +0100
X-SpamFlt-Status: Not Detected
X-KASFlt-Status: Rate: 0
X-KASFlt-Status: Status: not_detected
X-KASFlt-Status: Method: none
X-KASFlt-Status: Envelope from:
X-IronPort-Anti-Spam-Filtered: true
X-KASFlt-Status: Profiles 14082 [Jun 09 2010]
X-KASFlt-Status: Version: 4.0.6
X-MimeOLE: Produced By Microsoft MimeOLE V6.1.7600.16543
X-IronPort-Anti-Spam-Result: ApsEAHssD0zVomGh/2dsb2JhbACfN70phRgE
Received: from just-the-name.co.uk (HELO mail.just-the-name.co.uk) ([213.162.97.161])  by relay.ptn-ipout02.plus.net with ESMTP; 09 Jun 2010 13:56:47 +0100
versus
Received-SPF: None identity=pra; client-ip=84.92.2.97;  receiver=mx.ptn-ipin04.plus.net;  envelope-from="xxx";  x-sender="xxx";  x-conformance=sidf_compatible
Received-SPF: SoftFail identity=mailfrom; client-ip=84.92.2.97;  receiver=mx.ptn-ipin04.plus.net;  envelope-from="xxx";  x-sender="xxx";  x-conformance=sidf_compatible
Received-SPF: None identity=helo; client-ip=84.92.2.97;  receiver=mx.ptn-ipin04.plus.net;  envelope-from="xxx";  x-sender="postmaster@relay.ptn-ipout02.plus.net";  x-conformance=sidf_compatible
X-SBRS: 5.1
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AmsBAAIsD0xUXAJhl2dsb2JhbACeWwEBAQEBCBUHM70ghRgE
X-IronPort-AV: E=McAfee;i="5100,188,6007"; a="3582482"
X-IronPort-AV: E=Sophos;i="4.53,391,1272841200";    d="scan'208";a="3582482"
Received: from mx.ironport.plus.net (HELO relay.ptn-ipout02.plus.net) ([84.92.2.97])  by mx.ptn-ipin04.plus.net with ESMTP; 09 Jun 2010 13:56:47 +0100
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: ApsEAHssD0zVomGh/2dsb2JhbACfN70phRgE
Received: from just-the-name.co.uk (HELO mail.just-the-name.co.uk) ([213.162.97.161])  by relay.ptn-ipout02.plus.net with ESMTP; 09 Jun 2010 13:56:47 +0100
... a few more routing lines
... then
X-SpamFlt-Status: Not Detected
... another routing line
... then
X-KASFlt-Status: Version: 4.0.6
X-KASFlt-Status: Envelope from:
X-KASFlt-Status: Profiles 14082 [Jun 09 2010]
X-KASFlt-Status: Rate: 0
X-KASFlt-Status: Status: not_detected
X-KASFlt-Status: Method: none
So... any idea what is happening?

[#2]

Might be worth seeing what happens if you turn off the Kaspersky filtering and rely solely on the Ironports?
Just a layman's thought!
Chris

[#3]

Interesting... OK... I'd assumed that the Kaspersky lines were  being generated by PlusNet.
I have Kaspersky running on my Windows PC(s), but I actually collect the mail using fetchmail on one of my Debian boxes which then provides an IMAP service to the other PCs.
So... perhaps the Kaspersky details are a red-herring and I'm just left with 'something' resending/redelivering emails?
dick:quote

[#4]

Fetchmail might be configured to preconnect with Kaspersky hosted security?  In any case, I reckon your problem is more likely to be caused by Fetchmail than by Plusnet -- or at least by a mismatch between them....  I don't really know much about it, though, so I hope some bright spark will wade in and help you!
Chris

[#5]

Quote from: hardya

Interesting... OK... I'd assumed that the Kaspersky lines were  being generated by PlusNet

Nope! Which leads me to concur with the suggestion that it's something local causing the problem.