Could you spell out in greater detail the steps you've gone through that precede this circumstance?
It sounds more like you're sending an image of the first page, or a print or perhaps a PDF rather than the actual Excel file.
So walk us through in detail the steps you've taken to
save the file to Excel
email it out
By emphasizing "in detail" I mean spell out menu clicks to save, filename used, extension in file name; similarly, how has it been emailed...attachment? How does it appear in the email? For example, here's a screen capture from an email to which I attached a spreadsheet. It's clearly an Excel spreadsheet, from the image and the file name......