Jordan and Steve both provided the full answers. I'd just like to add that there are some English speakers who will use the slang term "snail mail" when referring to postal mail, since that form of mail moves significantly slower than email.

Postal mail is called "mail". Electronic mail is called "email". There was a time when "e-mail" was correct, but that time is past. :) I would stick to those terms if I wanted to be clear.

All of them are used. To me, "e-mail" feels a bit old-fashioned: there are twice as many Google hits for "email" as there are for "e-mail." "Mail," of course, is less precise: it also refers to physical letters. Overall,my preference is "email." --Best, Chris H.

Mail usually refers to paper mail, sent through the postal system in envelopes. E-mail and email are two ways to spell the same thing. Email is used much more commonly, but neither is seen as improper. Email is never called just "mail", it would confuse people. I hope this helped you!

"Email" is the same thing as "E-mail", I believe some people leave out the dash, only due to the fact that they are lazy, or don't know how to use punctiation, diacritics, or other accents in general. It really just goes unnoticed, and has gotten to the point where it is correct either way.