The content of the Validation email is not encoded properly on Outlook

Steps to reproduce:

• activate the SMTP server on your wiki
• enable "Use email Verification" and "Authentication Active Check" from the wiki administration, "Registration" section
• create a new user with the first name and last name containing accents (e.g. élena oanà) from the registration form (e.g. http://localhost:8080/xwiki/bin/view/XWiki/Registration)
• open the activation email on Outlook
  Result
• the accents are not encoded on Outlook