Can you specify where you're getting the error? Is it from FMP or from your email client or from e-vite? The more informatin you can give us the better we are to help you. Thanks!
Nick is right, we need more details.
Filemaker does have specific encoding that may be incompatible, but you are able to select different encoding for your files. You'll need to check with e-vite to see if it has any encoding specifications. Also, it may be worth it to try a different file format.
AFAIK, the CSV is fairly standard, or at least should be in your case of name/email as your fields.