No, you cannot connect them that way just by themselves. You would need a cellular or wifi signal to send the email. But, if you are like me, anytime I have my iPad with me, I also have my iPhone. My iPad is wifi only, and in those instances where I have no wifi, I just use my iPhone. But, I avoid paying the ridiculous (IMO) extra monthly fee for tethering, nor do I pay for cellular on the iPad.
Most of the time I ever use my iPad, I find I'm within range of a wifi node I can use, and for the few times I'm not, I just use my iPhone itself for email or web or whatever I need. If money is a real concern, and you already have a smart phone with data plan, it may be possible to just avoid any extra connection fees of any kind with the addition of the iPad.
Depends on your budget, where you are and how you use your device(s), but worth thinking about a bit before buying any tablet. Tethering, to me, only makes sense if you really use it a lot every month - otherwise, your are paying a great deal for something you are not using.