There is a known bug with Outlook 2010 and 2013 that causes Non Delivery Reports (NDR) to be converted to Chinese-like characters when they are forwarded:
The same NDR does not get converted when being forwarded using OWA or when forwarded as an attachment.
The good news is that there are updates to fix this:
- Outlook 2010: February 9, 2016, update for Outlook 2010 (KB3114756)
- Outlook 2013: Forward of NDR in Outlook 2013 displays Chinese characters