Turn Off Regional Character Settings
When Outlook Web Access users use Internet Explorer 5 or later to send a message, recipients who have mail clients that are not Unicode Translation Format-8 (UTF-8) aware cannot view the message. A workaround for this problem is to disable regional characters.
Warning Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.
For information about how to edit the registry, view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it, and you should also update your Emergency Repair Disk (ERD).
To disable regional character settings:
Note More information is available on the Microsoft Product Support Services Web site, in the Microsoft Knowledge Base article Q273615, “XWEB: Mail Clients That Are Not UTF-8 Aware Cannot View Messages Sent from Exchange 2000.”