Email container files (.pst, or .nsf archive files) don’t usually contain email header file names (from; to; cc; bcc; subject). Processing software will assign the header field names, and often use English terms by default regardless of the content of the messages. So even if you have emails in one or more foreign languages, threading analytics tools should always have English as one of the selected languages.
Forensic tools exist which can analyze email headers to find the IP address of the computer a message was sent from, and also the geographic location it was sent from. eMailTrackerPro is an example of a tool which performs this task. eMailTrackerPro will help you track the origin of all emails in a particular account.
If you want to check the header of an individual email without software, you can use Google Toolbox's Messageheader, available here: https://toolbox.googleapps.com/apps/messageheader/