Good afternoon. I have been having this issue and it was when I was investigating it that I saw that many people seem to have it yet there are very few solutions. My colleague and I have found one that worked for us.
In our instance the issue was caused by a missing Font (Arial Narrow) but corrupt fonts can cause the same issue. We tracked this down by examining the make up of the email which opens up in a notepad file.
Stop and disable the following services:
Windows Font Cache Service
Windows Presentation Foundation Font Cache 3.0.0.0
Reboot the machine otherwise the next steps won't work.
Browse to**:**C:\Windows\ServiceProfiles\LocalService\AppData\Local
and delete any .dat files that start with "FontCache" and also make sure the "FontCache" folder is empty.
Browse to the PC from another PC on the network and delete the offending fonts from C:\Windows\Fonts. It won't work if you try and delete it/them from the same PC. It'll give you an error message about how it's a "System Font" and "can't be deleted".
Once you've removed the fonts reboot the machine, Enable and start the two services above that you stopped and then open Word. Select your desired font from the drop down menu. If there's a cloud symbol there that means your font isn't installed and will be
installed from the cloud. Select it and begin typing. That should be it!
Simon.