On a tablet can you e-mail from Europe to the US - with Wi-Fi?
Can you e-mail from Europe to the US - provided you have Wi-Fi?
That answer really depends on your email provider. Internet will work as long as you have an available connection. If you use a local ISP for your email, you'll need to ask your provider for any limitations. If you use Gmail, yahoo, or most other free email providers you'll generally have no problems sending emails while you're in Europe.