Isso pode ser um problema de formatação ... Para corrigir, acho que você deve tentar configurar o Unicode UTF-8.
Click the orange "File" tab in the top left corner of the Outlook 2010 window and click "Options" on the pull-down menu. A new window titled "Outlook Options" appears.
Click the "Advanced" heading on the left side of the window and then scroll to the "International Options" heading near the bottom.
Place a check in the box labeled "Automatically select encoding for outgoing messages" and click "Unicode (UTF-8)" on the drop-down menu.
Place a check in the box labeled "Automatically select encoding for outgoing vCards" and click "Unicode (UTF-8)" on the drop-down menu.
Place a check in the box labeled "Allow UTF-8 support for the mailto: protocol."