There’s a lot you can do using e-mail, including upload FTP files, create home pages, send snail-mail, translate languages, play games (blank e-mail), send a fax (no subject, “help” in body), track webpage changes, etc. The full details are available at the Accessing the Internet by Email FAQ
Things you can use e-mail for
Use email for more than just messages. You can upload files via FTP, create home pages, send faxes or snail-mail, translate text, and track website changes by interacting with specialized mail servers and gateways.