Mail in OS X 10.10.2: Removing attachment makes message unreadable

Question

OS X 10.10.2, Mail 8.2 (2070.6)
While in previous versions sometimes message attachments were not recognized and could not be removed, this has improved in the actual version.
Now a new problem arose: Sometimes, removing the message, recodes the text such as it becomes completely unreadable.
Example:
嗁テig拆.畕�呴毑h湲�(~�(汏テig瞼.畕�呴毑h湲�(~�(殗邏迁}鴾{���汗靣�散r�,←\�~'�聤萜ig瞏!囤!zf瑲'+⑹�凳&䥽邏 强跰8�]竣iテig� m稛�� 0迠帻4D@《ix��歷g璲�mリ畩��^炘颔�(炞Т�^七岫i\叒靭�.��&z支jg��檗h'甸��葴畫(~炸x~)mz窛欑b簁-蔠��夗 玮�+b?~夗}��~夗}� 殩&電枾⑶帝^y踡高n�_i菬_jhド6、f﹋z,{]底�7鐜6泗W儁娯祥2� ⒐殩X尣僪甪+滩僪甪妢�歠珎)邰踙汳4譀_l�7帝Jm~夗}�$鈾� {�h櫓靭笩jX蔤溗(�*^甔k(曹氣⒏運+n[灥靘u�(b赍妛毦+"电lォ滩侐リ鍔y�h羚f矉-蔠┊*+娷锦�%⒑n畽^奠mu�(b 赍妛┠櫒堀{^娌�-蔠棭z�(潻kz檙~夗}� 殩&電僻睬珘�(枈��弡 �( �Cy霎栙藃曤rョ宝婍r~夗�,拮M)稏爕j+u'湺*'秩硔璿覜{鱩)秄珎)餮啥焉费啥焉潑酲瀝亘焃Z佸ō詾r亘焈旆)^夬-zk(��ア萙ョ^}端奁�� v+l�'fk�5觧���wb~'嗟楝＼f枊!j棩k*.恩贝�潑�"vf┙靘�鏱抵環 䦆!j棩k*.伏f曢輭�醳≤x�  b濦�栫瘱)��洬潑�%j��Z娸I�-妷酯蒢怖 矁h甪ゲ枾暕��CTJ藃曕�l�7底Jm~夗}�*袣�&電东ǘ僻睬珘⒆(枈��弡 7毉〆瑙�)j楗蒢怖 矁h甪ゲ枾暕��CTJ藃曕�l�7底Jm~夗}�*袣�&電东ǘ僻睬珘⒆(枈��弡�奼n�欹��%j��2� ⒐殩蔤濾� Q+-蔠�~夗�,拮])碟'钓\婤jX洰*诋③�炈��'旰媆+証=�4醞y2㈢璇*.h畫爣 +拪欹��%j��2� ⒐殩蔤濾�
The header and the start of the text (some parts removed due to privacy)
Return-Path: [removed]
X-CGP-ClamAV-Result: CLEAN
X-VirusScanner: Niversoft's CGPClamav Helper v1.18.5 (ClamAV engine v0.98.5)
Received: [removed]
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: A0AjAwAzXOtUnFfqN51bgkMhdFoEgwS7Z4obAhyBSgEBAQEBARABAQEBAQYNCQkULoQPAQEBAQMSARA KXAIBCA4DBAEBCx0DAgICMBQJCAEBBBMIGogNAQIBrGoBgTxfBYsAAQFvmBQBAQEBAQUBAQEBAQEBAQE ZixOEDBEBVoJpL4EUBZowhUCJGoM+hBBvgQs5fwEBAQ
X-IPAS-Result: A0AjAwAzXOtUnFfqN51bgkMhdFoEgwS7Z4obAhyBSgEBAQEBARABAQEBAQYNCQkULoQPAQEBAQMSARA KXAIBCA4DBAEBCx0DAgICMBQJCAEBBBMIGogNAQIBrGoBgTxfBYsAAQFvmBQBAQEBAQUBAQEBAQEBAQE ZixOEDBEBVoJpL4EUBZowhUCJGoM+hBBvgQs5fwEBAQ
X-IronPort-AV: E=Sophos;i="5.09,631,1418079600";
   d="scan'208,217";a="28634691"
Received:[removed]
Received:[removed]
Received:[removed]
Received:[removed]
Received: [removed]
From: [removed]
To: [removed]
Subject: [removed]
Thread-Topic: [removed]
Thread-Index: AdBMRHx2jNWtUCFcR0iWrwUrE02J6wAEKdCgAMp/94AAAtO3IA==
Date: Mon, 23 Feb 2015 17:02:48 +0000
Message-ID: <[email protected]>
References: <[email protected]>
<[email protected]>
<[email protected]>
In-Reply-To: <[email protected]>
Accept-Language: da-DK, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.87.1.44]
Content-Type: multipart/alternative;
  boundary="_000_C2FB31364A05CD4C86D4FEBE2FAC02777B3810BFSRVUNIMBX05unia_"
MIME-Version: 1.0
Return-Path: [removed]
X-EOPAttributedMessage: 0
Received-SPF: None (protection.outlook.com: mbg.au.dk does not designate
permitted sender hosts)
Authentication-Results:[removed]
(message not signed) header.d=none;
X-Forefront-Antispam-Report:
  CIP:185.45.20.64;CTRY:EU;IPV:NLI;EFV:NLI;SFV:NSPM;SFS:(10009020)(428002)(252514 010)(199003)(189002)(97736003)(107886001)(2656002)(19580405001)(19580395003)(159 75445007)(68736005)(19625215002)(102836002)(87936001)(6806004)(64706001)(2900100 001)(16236675004)(2950100001)(512874002)(2920100001)(105586002)(54356999)(761769 99)(92566002)(106466001)(33656002)(84326002)(5250100002)(101416001)(50986999)(10 4016003)(55846006)(74482002)(450100001)(77156002)(62966003)(110136001)(53416004) (46102003)(19300405004)(7099025);DIR:OUT;SFP:1101;SCL:1;SRVR:VI1PR01MB0846;H:SRV UNIHUB01.uni.au.dk;FPR:;SPF:None;PTR:InfoDomainNonexistent;A:1;MX:1;LANG:en;
X-Microsoft-Antispam: UriScan:;
X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;SRVR:VI1PR01MB0846;
X-Microsoft-Antispam-PRVS:
  <[email protected]d.exchangelabs. com>
X-Exchange-Antispam-Report-Test: UriScan:;
X-Exchange-Antispam-Report-CFA-Test:
  BCL:0;PCL:0;RULEID:(601004)(5005003);SRVR:VI1PR01MB0846;
X-Forefront-PRVS: 0496DF6962
X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:;SRVR:VI1PR01MB0846;
X-OriginatorOrg: mbg.au.dk
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Feb 2015 17:02:49.7593
(UTC)
X-MS-Exchange-CrossTenant-Id: 61fd1d36-fecb-47ca-b7d7-d0df0370a198
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=61fd1d36-fecb-47ca-b7d7-d0df0370a198;Ip=[185.45.20.64]
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR01MB0846
--_000_C2FB31364A05CD4C86D4FEBE2FAC02777B3810BFSRVUNIMBX05unia_
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
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Answer 1

I've used the "remove attachments" feature regularly for years. No problem. Got on Yosemite and now... getting this mess.
I'm using IMAP so I think... just access my mail via webmail or another device. Wrong. The message is ruined for all time there too.
This is business-related email. In some cases a legal record of a conversation is now lost.
In the graphics / video business, leaving all attachments in my email account is not an option.
One Helpful Tip:
You can still view the text of the original message by going to View > Message > Raw Source.
V5k