It's hard to be sure because you don't indicate what *does* happen when the
recipient tries to open it, whether these are Mac or Windows users, nor do
you disclose any details pertaining to the email specs you or the recipients
are using. You may be doing nothing wrong at all. It could be a problem with
your email service or that of the recipients.
With nothing to go on though, the only suggestions I can offer are:
1- Make sure you're saving the Excel files to include the filename
extensions (.xls, .xlsx, etc.),
2- Confirm that whatever email software you're using is properly configured
for encoding attachments,
3- Zip/Stuff your files before attaching & send that copy.
HTH |:>)
Bob Jones
[MVP] Office:Mac