Why can I not open multipart doc files?

I have a DOC file which was produced by Confluence which can be opened perfectly with Word under Windows, but cannot be opened in LibreOffice. The file is completely “readable” text and starts with something which looks like very much an email body.

Message-ID: <1630420246.1792.1510059714000.JavaMail.confluence@collab>
Subject: Exported From Confluence
MIME-Version: 1.0
Content-Type: multipart/related; 
	boundary="----=_Part_1791_1613363931.1510059713998"

------=_Part_1791_1613363931.1510059713998
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Content-Location: file:///C:/exported.html

<html xmlns:o=3D'urn:schemas-microsoft-com:office:office'
      xmlns:w=3D'urn:schemas-microsoft-com:office:word'
      xmlns:v=3D'urn:schemas-microsoft-com:vml'
      xmlns=3D'urn:w3-org-ns:HTML'>
<head>
    <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Dutf-8=
">
    <title>Digital Ocean &amp; Ocean Media Lab - 6P (19200 chars)</title>
    <!--[if gte mso 9]>
    <xml>
        <o:OfficeDocumentSettings>
            <o:TargetScreenSize>1024x640</o:TargetScreenSize>
            <o:PixelsPerInch>72</o:PixelsPerInch>
            <o:AllowPNG/>
        </o:OfficeDocumentSettings>
        <w:WordDocument>
            <w:View>Print</w:View>
            <w:Zoom>90</w:Zoom>
            <w:DoNotOptimizeForBrowser/>
        </w:WordDocument>
    </xml>
    <![endif]-->
    <style>

Do you have any idea why this happens and what I can do to get a readable file.

Thanks
Reiner

(I am not at all an expert here! Don’t know Comfluence, have no ‘Word’, rarely create html-files with LibO.)
Did you already try to open the file with a plain text editor and to clip the first few lines so the file then starts with <html and keeps all the rest. Saved with this slightly reduced content it might actually be correct standard html and LibO Writer would then be able to open and edit it.
Html tags and attributes LibO doesn’t understand will be ignored then.

It looks like that word thinks it is a Microsoft Word 97 - 2003 Document. However, when I select “save as …” the pre-chosen option is “Website in a File”. Is there an option to open such documents?

(This surely isn’t an answer. To add to your original question you should better edit it.)

LibO can read html and save text files to html within reason. It is not a full-featured html/web editor. The few web pages I made I used LibO for, however. If you create a new ‘HTML Document’ with LibO some differences are obvious.