As of the completion of the sendgrid acquisition, there is no email verb for twiml. Your only options are to host code on a third-party and call it from Twilio (sendgrid could be that Third party) or write a Twilio function.
But the easiest way to do this, by far, would be a simple email verb in Twiml. No dice so far…
I don't want to host offsite code or write complicated functions just to CC: an SMS to my email inbox ...
A <email> twiml verb would be simple and useful.