Some users use .oft for sending out emails. They are templates that have been created to insure uniformity when sending emails.
A user might get an error message when trying to open one.
This is being caused by an Adobe plugin in 99% of cases and the solution is straight forward
You are going to go in to the users Outlook application and check to see if they have this plugin
**Adobe Send and Track for Microsoft Outlook - Acrobat**
FILE -> Options -> Add-ins --> Manage COM Add-ins --> Go. Then uncheck "Adobe Send & Track for Microsoft Outlook - Acrobat" --> OK.

If they have this plugin simply uncheck it, restart outlook and try to open the .oft file again