E-mail software provider IncrediMail found that nearly 90 percent of 10,000 survey respondents have used an emoticon, smiley face or animated character to enhance an e-mail. For some, emoticons are still the mark of an unprofessional, lazy e-mailer. "It's like wearing shorts to a business meeting," says Jeremy Brandt, founder of FastHomeOffer.com, a marketing and lead-generation firm for residential real estate investors. "If you're lazy in your e-mails, are you going to be lazy in your business dealings, too?"

Others take a situational tack: The propriety depends on the relationship between e-mailer and e-mailee. Thirty-five-year-old Jared Smith, co-founder of Tempe, Arizona-based BlueMedia, a vehicle wrap and large-format graphics firm with 2007 sales of about $5.8 million, finds that with some work relationships, emoticons make sense: "We have clients who want to have lunch and know how your kids are doing. I've found myself putting a smiley face at the end of [an] e-mail to convey the emotion necessary to build that rapport." But he's careful to keep it all business with more formal contacts.

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Will Schwalbe agrees that it's all about reading cues. "You should never [use emoticons] in your first communication with someone," says Schwalbe, who co-wrote Send: The Essential Guide to Email for Office and Home with David Shipley. "If you consistently use emoticons and the person you're writing to doesn't, that's their way of telling you you're probably being too casual." Schwalbe also advises never to use emoticons sarcastically or in formal situations, such as in an e-mail to a banker, compliance officer or attorney.