After interviewing a college student in June, Tory Johnson thought she had found the qualified and enthusiastic intern she craved for her small recruiting firm. Then she received the candidate's thank-you note.

It was laced with words like "hiya" and "thanx," along with three exclamation points and a smiley-face emoticon.

"That e-mail just ruined it for me," says Ms. Johnson, president of New York-based Women for Hire Inc. "This looks like a text message."

Hiring managers such as Ms. Johnson say an increasing number of job hunters are just too casual when it comes to communicating about career opportunities. Thank-yous on paper aren't necessary, but some applicants are writing e-mails that contain shorthand language and decorative symbols, while others are sending hasty and poorly thought-out messages to and from mobile devices. Job hunters are also using social-networking sites such as Facebook and MySpace to try to befriend less-than-willing interviewers.

These incidents typically involve college students and recent graduates, and recruiters say such faux pas can be instant candidacy killers because they hint at immaturity and questionable judgment.

The trend may reflect a cultural divide between younger and older workers, says David Holtzman, author of Privacy Lost: How Technology Is Endangering Your Privacy. Workers in their 20s and younger are accustomed to online and cellphone messaging and to the abbreviated lingua franca that makes for quick exchanges, he says. "It's just natural for them. They don't realize that it's perceived to be disrespectful."

Travis Hawk, a May graduate of Drake University, says he prefers text messages to phone calls and almost fell victim to his text-lingo behavior in e-mails to recruiters during his recent job search. "I had to focus on not doing it," says the 23-year-old, who just got an entry-level sales position at Principal Financial Services Group. Now an intern at the Des Moines, Iowa, firm, he says his penchant for using abbreviations such as "r" for "are" is sometimes hard to manage.

Other job hunters, however, don't see any need for restraint. Smiley faces, hearts and other icons appear in about one of every 10 thank-you e-mails sent to hiring managers at KPMG LLP, says Blane Ruschak, the New York accounting firm's national director of university relations and recruiting.

But KPMG's staffing specialists, who hire about 2,700 college graduates and 2,300 interns annually, are not amused. "We don't feel emoticons have a place in any formal communications," says Mr. Ruschak. "It's not professional."