Root Cause:
When retrieving an email with an attachment whose filename includes non-Latin characters, the filename extension is altered from .docx to .doc x (This issue is orginates from Microsoft side)
Fix:
We will change the received extension to proper extension while decoding the filename.
Note: This is a temporary fix jar only for CX #9178069.
Check the "Jar Compatibility" section to download the appropriate fix jar file (.fjar file). Check this link on how to apply the fjar file. 
Jar Compatibility
Build No | File Name |
14502 | 14502_9178069.fjar |