If you email someone a document, created in some fancy proprietary file format, don’t be surprised if it doesn’t get read.
In this day and age, there is no reason why a file cannot be an Adobe PDF, a Word doc wrapped in a zip file, or a non-macroed spreadsheet. Acrobat Reader is free, and everyone has a copy of Word and Excel (if you don’t, get OpenOffice..its free too, and it reads everything created using Microsoft Office).
But if you create that valuable piece of information in some program you wrote yourself, compiled in Cobol on a VAX, and used a “.nobodywillknowwhatthehelltodowiththisfile” extension, don’t expect it to be of much use.
I certainly won’t read it.