By the way, Campbell believes that e-mail should be written "email," no hyphen.
Hyphens are for new words just entering the vernacular; at this point, e-mail has become so entrenched in the language that its hyphen, the linguistic equivalent of training wheels, should be discarded, Campbell said.
This is what Bill Walsh of the Washington Post has to say about the matter:
Compound nouns do tend to go from separate to joined, often (though not so often anymore) with a hyphen stage. The problem with "e-mail" is that it's not a simple compound noun. It's an initial-letter-based abbreviation, and no initial-letter-based abbreviation in the history of the English language has ever morphed into a solid word. The "e" isn't simply a syllable -- it's the letter e, for Chrissakes, like the X in "X-ray." Nobody lives in an "aframe," nobody drives a "zcar," and you will find no example parallel to the illiteracism "email." "Email" (the French word for "enamel," by the way) divorces the e, ee, eee! so that the first syllable begs to be a schwa sound. Uhmail. Uh.
We're with Bill on this one. E-mail, people. E-mail.