An update has been released for Outlook 2013 and can be downloaded and installed manually, but is also being offered via Microsoft Update.
Update KB2738013 for Outlook 2013
This is a non-security update which solves 3 issues all related to Outlook.com accounts.
- The content of Outlook items may not be displayed correctly when composing them with anything other than UTF-8 encoding. This update also requires update KB2768007 for Word 2013 to be installed.
- Mail items may appear as duplicates in Outlook. Deleting the duplicate in Outlook will however also delete the original on Outlook.com.
- Email messages that contain non-ASCII characters are not displayed correctly.
If you have Microsoft Update configured to also update other Microsoft applications, then this update will also also be offered via Microsoft Update or has already been updated automatically for you.