Gmail – Why aren’t ics attachments send to the IEEE address working in Gmail anymore

When I get emails about appointments from our Outlook server, they attach a .ics file to the email which contains the account details. This used to work fine, giving me the option to add the event to my Google Calendar.

However, now this only works if the email is sent directly to my Gmail account, and not when I use my ieee.org forwarding email address (which just forwards to Gmail).

If I send the invite to my Gmail address, the calendar event is automatically added to my Google Calendar, and I am given the option to respond in the email. In this case the raw email (without tx details) looks like this:

From: David Dean <xxxx@qut.edu.au>
To: "xxxx@gmail.com" <xxxx@gmail.com>
Date: Thu, 23 Jun 2011 09:52:36 +1000
Subject: Test
Thread-Topic: Test
Thread-Index: AcwxN3ZO6sDlD9SYT1KvfHhbcj4GVw==
Message-ID: <0A52784B9330A94A9357569C34E81F5E92C4AA80BB@QUTEXMBX03.qut.edu.au>
Accept-Language: en-US, en-AU
Content-Language: en-AU
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: en-US, en-AU
Content-Type: multipart/alternative;
    boundary="_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BBQUTEXMBX03qut_"
MIME-Version: 1.0
Return-Path: d.dean@qut.edu.au

--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BBQUTEXMBX03qut_
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64

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--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BBQUTEXMBX03qut_
Content-Type: text/calendar; charset="utf-8"; method=REQUEST
Content-Transfer-Encoding: base64

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--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BBQUTEXMBX03qut_--

However, if I forward the email through my ieee.org email address, The only thing I see in the email is the details of the appointment in text (and sometimes not even that). I certainly don't get any Google Calendar integration. The raw text in this case is:

From: David Dean <xxxx@qut.edu.au>
To: "xxxx@ieee.org" <xxxx@ieee.org>
Date: Thu, 23 Jun 2011 09:53:42 +1000
Subject: TEst2
Thread-Topic: TEst2
Thread-Index: AcwxN52gf7e8V9MZRjux1SIjrpggsg==
Message-ID: <0A52784B9330A94A9357569C34E81F5E92C4AA80BC@QUTEXMBX03.qut.edu.au>
Accept-Language: en-US, en-AU
Content-Language: en-AU
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
acceptlanguage: en-US, en-AU
Content-Type: multipart/alternative;
    boundary="_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BCQUTEXMBX03qut_"
MIME-Version: 1.0
X-Spam-Score: undef - spam scanning disabled
X-CanIt-Geo: ip=131.181.191.3; country=AU; region=04; city=Brisbane; latitude=-27.5000; longitude=153.0167; http://maps.google.com/maps?q=-27.5000,153.0167&z=6
X-CanItPRO-Stream: ddcc (inherits from 90_OPT_OUT,default)
X-Scanned-By: IEEE Spam Scanner (https://uce.ieee.org/) on 140.98.193.230

--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BCQUTEXMBX03qut_
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64

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--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BCQUTEXMBX03qut_
Content-Type: text/calendar; charset="utf-8"; method=REQUEST
Content-Transfer-Encoding: base64

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--_002_0A52784B9330A94A9357569C34E81F5E92C4AA80BCQUTEXMBX03qut_--

Other than some minor differences in the name and time of the events, the main difference appears to be

--- to xxxx@ieee.org
+++ to xxxx@gmail.com
-X-Spam-Score: undef - spam scanning disabled
-X-CanIt-Geo: ip=131.181.191.3; country=AU; region=04; city=Brisbane; latitude=-27.5000; longitude=153.0167; http://maps.google.com/maps?q=-27.5000,153.0167&z=6
-X-CanItPRO-Stream: ddcc (inherits from 90_OPT_OUT,default)
-X-Scanned-By: IEEE Spam Scanner (https://uce.ieee.org/) on 140.98.193.230
+Return-Path: d.dean@qut.edu.au

If this is the difference that is causing the problem (I may have missed something, I guess), then why would the addition of these extra headers cause Gmail to not integrate with Calendar on these messages any more.

I'm also interested in what has changed, because this used to work. It looks like older emails send through my IEEE address that I know had Calendar integration at the time no longer do, so I suspect that it is Gmail that has changed, and not IEEE.