Most of the technical world uses "email" not "e-mail".
From the wikipidea, According to the Microsoft Manual of Style for Technical Publications Version 3.0:
Okay to use to refer to an electronic mail program, as in "check your e-mail for messages," but use e-mail messages, or just messages or notes, to refer to pieces of e-mail. Do not use e-mails.
In formal communications, avoid use as a verb, as in "e-mail the file." Instead use "send" or "send an e-mail".
Spelling of this term is disputed, and varies by field. While "e-mail" (with a hyphen) is used in journalism (such as by the CNN, BBC and New York Times), the computer industry primarily uses the spelling "email" (no hyphen). In particular, the original spelling is "email" (no hyphen), based on the technical roots of the term, as seen in the RFC documents for SMTP, POP and IMAP, which use "mail" or "email".
While some businesses, including Microsoft, use "e-mail", the non-hyphenated spelling "email" is more common in the computer industry. For example, Google, Yahoo, eBay and Apple use "email".
"Email" without a hyphen is preferred by 4 to 1 among people who work with email technically, as can be seen by comparing the Google search results for "email headers" and "e-mail headers".
When attempting to search Google using keyword phrases containing: "e-mail" it attempts to correct your spelling 8O
As of Feb, 06, these are the search results from the most popular search engines for email versus e-mail:
- Yahoo: 'email' = 3,430,000,000 / 'e-mail' = 2,410,000,000
- Altavista: 'email' = 3,440,000,000 / 'e-mail' = 2,410,000,000
- Google: 'email' = 2,260,000,000 / 'e-mail' = 1,870,000,000
- MSN: 'email' = 596,699,110 / 'e-mail' = 474,126,191
- Lycos: 'email' = 518,620,000 / 'e-mail' = 276,720,000