Mail: Deal with winmail.dat files sent by Outlook

[Nils160988]

Feature Request

Outlook sometimes sends e-mail attachments encapsulated in a file named "winmail.dat". It would be nice to be able to extract the attachments from "winmail.dat".

---

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[ChristophWurst]

I'm very hesitant adding support for a vendor-specific, proprietary format if it's not specific in any RFC or so.

[Nils160988]

I know what you mean and I understand it. Unluckily, you are sometimes forced to deal with these things, so if someone has an idea and is willing to implement it, it might be a nice addition.
If you don't think so, feel free to close it here.

[ChristophWurst]

Let's leave it open for a while. We'll see if anyone else shows interest.

[DavidDohmen]

Probably fitting in this topic:
Outlook sometimes sends calendar invite files without the ".ics" ending, which in turn don't get detected by Nextcloud Mail. Is there already another issue for this open, or should i open one, with a bit more detail?
I also mentioned it in this reddit thread:
https://www.reddit.com/r/NextCloud/comments/fq211k/nextcloud_mail/

[ChristophWurst]

I'd be curious to know the mime type of that attachment. Could you inspect the message source with another client?

[DavidDohmen]

Hi Christoph!
In Geary and Evolution (Gnome) I can see the file attachement.
Viewing the source of the email in Geary yields this information:

`Return-Path: [e-mail]
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: from EUR05-AM6-obe.outbound.protection.outlook.com (mail-am6eur05olkn2100.outbound.protection.outlook.com [40.92.91.100])
by XXXXXX.netcup.net (Postfix) with ESMTPS id 16B32A246E
for [e-mail]; Mon, 23 Mar 2020 20:41:33 +0100 (CET)
Authentication-Results: XXXXXXX;
dkim=none header.[email protected];
spf=pass (sender IP is 40.92.91.100) smtp.[email protected] smtp.helo=EUR05-AM6-obe.outbound.protection.outlook.com
Received-SPF: pass (XXXXXXX: domain of live.de designates 40.92.91.100 as permitted sender) client-ip=40.92.91.100; [email protected]; helo=EUR05-AM6-obe.outbound.protection.outlook.com;
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;
b=hpK2hAC2vC9PCV8C5P/80mOrdn6omGfT8t53yB09dSOcxbyfjOdYMH/DKGmgDzeZ2Tq/D7lEHHARl5yWrTrNgIz3VHvTgmx1PR6yYg/TUKB8ELHC479tT12z6M+AohGds4z4nH8OMMRt5y9oVEsGsEj/EP5VmlWw8h4eMAvhvVlANR3OAYlvVy0f1ic0B+yklKquSMH4EoAIiGAXwicu3hCWmF8Mdde8osZS70QIZZ+C4p7pVJKyzpEHpSSvSXgWvYPeazR4HV2iZL6Uyfjv9pE9mUGXjnVFr8c0LT8Fdiln+S4n3QDBAE1i/Z8B1p6ejWuHBu/WlpsPgDX0M6XMoQ==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;
s=arcselector9901;
h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
bh=wRDd3lfUkwqklN3tdAjUXH2SpdFmEdSqeGf1lFuj8wg=;
b=b19eRln4KdMmkdxw3ouIZ+5I3m6zgHw2NyffYRaI4q+bQUDqhkA9QpwHfBbYs+wF/MCwFqFNlMttFejU8v4iQGbwM6888mdnLNt4acfqYDeoQQFrgA4PLt6kByiqHFrjC6/9FXqOcQOKGlfRCwbh2yPwKwuK7B3cNeX4+gJxkgSSMQsOPYyxY1E50wBuN1l1rsyuotYJGSK7Z8Oytk67I0i/kxbe2hyLr2+YktBk2c73r9Mrb+bFouVM+myPMj+/VOlyzJXJIwafc48LSOSYMchrEHlubXKaMhYUwb1WSUc/d2BHcgzJt7OdlB/uNMp9zga9CBQGn2upnfazQqDBQg==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none;
dkim=none; arc=none
Received: from AM6EUR05FT029.eop-eur05.prod.protection.outlook.com
(2a01:111:e400:fc11::39) by
AM6EUR05HT238.eop-eur05.prod.protection.outlook.com (2a01:111:e400:fc11::364)
with Microsoft SMTP Server (version=TLS1_2,
cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2814.13; Mon, 23 Mar
2020 19:41:30 +0000
Received: from AM0PR08MB4212.eurprd08.prod.outlook.com (10.233.240.54) by
AM6EUR05FT029.mail.protection.outlook.com (10.233.240.74) with Microsoft SMTP
Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
15.20.2814.13 via Frontend Transport; Mon, 23 Mar 2020 19:41:30 +0000
Received: from AM0PR08MB4212.eurprd08.prod.outlook.com
([fe80::7de1:cc9d:e877:ed07]) by AM0PR08MB4212.eurprd08.prod.outlook.com
([fe80::7de1:cc9d:e877:ed07%6]) with mapi id 15.20.2835.021; Mon, 23 Mar 2020
19:41:30 +0000
From: XXXXX [e-mail]
To: "[email protected]" [e-mail]
Subject: test3
Thread-Topic: test3
Thread-Index: AdYBSww81jyQkV+WC06I4Vn7YHYbaQ==
Date: Mon, 23 Mar 2020 19:41:30 +0000
Message-ID:
[e-mail]
Accept-Language: de-DE, en-US
Content-Language: de-DE
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-ms-publictraffictype: Email
x-incomingtopheadermarker:
OriginalChecksum:EC3E3C254D3983C498E2CEB3B54D6AFC57F8AC4009C9B766844F923918C43E5F;UpperCasedChecksum:7ACED566A01AC7284DDA68376D016F7A50EF0BB994E046B5F5C093C611610881;SizeAsReceived:6969;Count:45
x-ms-exchange-calendar-series-instance-id:
BAAAAIIA4AB0xbcQGoLgCAAAAACeFTYMSwHWAQAAAAAAAAAAEAAAAO4buFsfEOBPhgiTCCTOnZY=
x-tmn: [dMKbe4mcSWvSHW4aiaAVHQnR2uWp00nw]
x-incomingheadercount: 45
x-eopattributedmessage: 0
x-ms-office365-filtering-correlation-id: a819223c-27b8-408b-3053-08d7cf622f24
x-ms-traffictypediagnostic: AM6EUR05HT238:MeetingMessage
x-microsoft-antispam: BCL:0;
x-microsoft-antispam-message-info:
9XMsvjQMHXipa/ID6CMvjtQpsk0jXgAjzOzkxFrCaphWWJBhMe5zZH0KoswpNjG/
x-ms-exchange-antispam-messagedata:
GQKH+P/qLjaeMZUBjx5w2ne9hKXhJlSc0yM/DOQqvRz90NGKSceNuhBEoBI5O5oORkBmVXCKe+gCGTB5ojhfat7OSlP52XKo9e4HKf4YBorXb+xjScZWBZ2zg5FDILnwMvacciTUfjBDbbHPUwklrA==
x-ms-exchange-transport-forked: True
Content-Type: multipart/alternative;
boundary="_000_AM0PR08MB4212871D08416758E92296EFECF00AM0PR08MB4212eurp_"
MIME-Version: 1.0
X-OriginatorOrg: outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a819223c-27b8-408b-3053-08d7cf622f24
X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Mar 2020 19:41:30.0470
(UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Internet
X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6EUR05HT238
X-NC-CID: 8pIw7NguBEnmYauJ6lsNWaqDTZER6Q/S6TAtB4VrZDUS

--_000_AM0PR08MB4212871D08416758E92296EFECF00AM0PR08MB4212eurp_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

--_000_AM0PR08MB4212871D08416758E92296EFECF00AM0PR08MB4212eurp_
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

--_000_AM0PR08MB4212871D08416758E92296EFECF00AM0PR08MB4212eurp_
Content-Type: text/calendar; charset="utf-8"; method=REQUEST
Content-Transfer-Encoding: base64
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VkNBTEVOREFSDQo=

--_000_AM0PR08MB4212871D08416758E92296EFECF00AM0PR08MB4212eurp_--
`

[ChristophWurst]

Content-Type: text/calendar

That is fine. But no content-disposition or name, thus I think our app just won't detect it as attachment.

[DavidDohmen]

Seems so. It doesn't work with "Microsoft Mail" either. In Geary at least I can see the file. Receiving this in Outlook obviously works and it seems like Thunderbird and Evolution implemented a fix - so they can also directly import this into their calendars.
Could such a fix also be added to Nextcloud Mail?
It's just such an extremely common case to receive calendar invites from Outlook.

[ChristophWurst]

I'm very hesitant adding support for a vendor-specific, proprietary format if it's not specific in any RFC or so.

:man_shrugging: I'm not sure

[DavidDohmen]

Don't want to be too nagging here... A fix would just have such a large and positive impact on the UX. Basically this is the one thing holding me back, moving my entire company over to Nextcloud Mail and I'm pretty sure this is a problem for others as well - especially in businesses.

I totally share your dislike for deviating from standards as Microsoft seems to do here but unfortunately they have such a market power...

Is there anything I could do to convince you? A poll, a bug bounty e.g.?

[ChristophWurst]

Is there anything I could do to convince you? A poll, a bug bounty e.g.?

Bug bounties only help the community contributors. As an employee of Nextcloud GmbH I can't accept them and thus I always put them on other tickets should I claim some.

If you have an enterprise subscription for you company we can of course prioritize this feature. I just lack the time to look into this at the moment. And I fully do understand this is important to you, but so are the many other feature requests for other users.

If I touch related code in the future I might have a look, but I can't promise it. Hope this is understandable.

Contributions are welcome any time. If you want to fix it yourself I can give some pointers to get started :)

[DavidDohmen]

Thanks for your thourough answer, Christoph. We're a startup and do not yet have the capabilities to opt for the enterprise edition but I will definitely closely consider this, once we're more liquid!
I also can't program PHP, so that would probably be a waste of time.

Anyway thanks a lot for your time to explain the situation to me. All your hard work is very much appreciated! We love what you're doing!

Stay save!

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dumblob]

Just want to express my preference to have at least the nonstandard calendar attachments supported in NextCloud mail.

Would it be possible (I mean technically) to make a separate NC plugin which would add such functionality to NC Mail (possibly together with winmail.dat)? I might ask some devs to take a look at this if it'll be viable.

[ChristophWurst]

there is no plugin infrastructure for this app. if it's supposed to work then from within the app.