Please consider Bug 61845 - Attachment ODF document" recognized as "text/plain" by auto detect.

[Rainer Bielefeld]

Hi all,

it seems that Auto Mime Type recognition is completely broken in Bugzilla
  <https://bugs.freedesktop.org/show_bug.cgi?id=61845>.
Please always correct mime type if necessary after you attached a file, 
and please leave a comment in the Bug if your experience is different to 
mine.

Discussion if required please on <libreoffice-qa at lists.freedesktop.org>

Best regards


Rainer