Please see:
https://redmondmag.com/articles/2018/01/02/exchange-online-email-internationalization.aspx
and
https://blogs.technet.microsoft.com/exchange/2017/12/27/eai-support-announcement/
Don
Don Hollander
Universal Acceptance Steering Group
www.uasg.tech
don.hollander@icann.org
Skype: don_hollander