Why can’t I simply email an xml file?

I swear, there are some days when I HATE using computers….I just bought a programmable mouse, and the profiles are xml files. I was building a profile for a program on my desktop, and then emailed the xml to myself to use on my laptop. The file shows up in my email screen as .xml, but when I download it, it comes out as an unusable .txt file. WHY???