This proceedure requires changing Filename Extensions.
For safety sake, please make a backup of the folder(s) containing the Emails you are wanting to work with!
I suggest working with one local folder at a time if you have multiple local folders (ex. Inbox, Sent, Junk, Archives etc.)
It is important that you follow the next step to the 'T'
* Open File Explorer and create a new folder on your C:\ drive, name the newly created folder Email_Backup.
Now, One Local folder at a time, copy the individual email(s) into the newly created Email_Backup folder, this is folder you will be working with.
1. Launch Control Panel > Folder Options;
2. From the Folder Options window, choose the View tab;
3. Scroll through the list making the following changes;
a. Show hidden files, folders and drives = 'Selected';
b. Hide extensions for know file types = 'Not Selected';
c. Hide protected operating system files (Recommended) = 'Not Selected'
4. Click Apply and OK
Open an elevated command prompt mode with full Administrators rights.
1. Click on Start and type CMD in Search box;
2. Press Ctrl + Shift + Enter, (click Yes if you are prompted by User Account Control)
The command prompt window should read C:\Windows\system32> with a flashing cursor.
1. Please type cd.. and press Enter
The command prompt window should change to read C:\Windows> with a flashing cursor.
2. Again type cd.. and press Enter
The command prompt window should change to read C:\> with a flashing cursor.
* Here is where it's important to have named and placed the working folder as I asked.
3. Next type cd Email_Backup and press Enter
The command prompt window should change to read C:\Email_Backup> with a flashing cursor.
4. Type ren *.eml *.mht and press Enter (note the spacing)
This will change the filename extension in batch format.
You should now be able to read the .mht files with Internet Explorer or your favorite Web Browser!
I hope this offeres a solution to your issue.