I don't think emailing receipt feature is there in Copper.
If you really really need it, I suggest install a pdf or xps document writer driver/software for your printer. It resembles a virtual printer device. Usually, most computers already have these. if not, you can easily install one from internet. When printing a receipt from Copper, select the pdf/xps document writer device in 'printer select' dialog. It'll save the pdf/xps document at the location you provide. Finally, send the receipt as an email attachment from your email client.