Hyphens, En Dashes, Em Dashes
Q. Apparently, the 17th edition of the Chicago Manual is opting for email over e-mail. I take it, then, that the 17th edition will also recommend Xray, Tshirt, Hbomb, Tbone steak. Don’t be ridiculous. Consistency requires the hyphen: e-mail.
A. Every good style manual contains exceptions that could be seen as inconsistencies but that are actually thoughtful adjustments for sense, readability, and usage. For instance, CMOS 7.85 (16th ed.) lists antihero but anti-inflammatory, coworker but co-op, midthirties but mid-July, promarket but pro-life. You will find that authoritative dictionaries like Merriam-Webster and American Heritage, as well as many fine newspapers, now also acknowledge or even prefer email.