Outlook has a hard time decoding the text plain mails sent by XWiki

It seems that we send text/plan mails without indicating explicitly the (UTF8) encoding:

Content-Type: text/plain

It works fine with GMail for example (I guess it's using UTF8 by default), but the result is not great on Outlook. I guess an easy way to fix it is being more explicit about the encoding of the content as follow:

Content-Type: text/plain; charset="UTF-8"