Striking the right tone in work emails can be stressful. How does one stay professional while showing you do, in fact, have a personality? But while we continue to mull over how many (if any) exclamation points are acceptable when you’re emailing your boss, a new study published in the journal Social Psychological and Personality Science has clear marching orders on what you definitely shouldn’t include in your digital missives: researchers found that not only did using smileys not make people seem warm, it actually made them seem less competent.

Researchers at Ben-Gurion University of the Negev, University of Haifa and Amsterdam University designed experiments to see how 549 participants from 29 different countries responded to the use of smiley face emojis (or similar emoticons, the press release for the study notes) in work emails. In one experiment, participants read an anonymous work-related email—some had smiley faces and some didn’t—and were asked to evaluate how competent and warm they thought the sender was.

While real smiles can increase perceptions of competence and warmth, according to the press release, the digital versions don’t have quite the same effect. Using smiley emojis didn’t make people seem warmer over email, and what’s more, using them had a negative effect on perceptions of competence.

“In formal business emails, a smiley is not a smile,” Dr. Ella Gilkson, a postdoctoral fellow at Ben-Gurion University’s Department of Management and one of the study’s co-authors, said in the press release.

While it might seem obvious that using an emoji in a formal business email isn’t peak professionalism, the study revealed how emoji-use goes beyond perception—it actually impacts how effective your communication is. When participants responded to emails that included emojis, they shared less information with the sender. Answers to emoji-less emails were “more detailed and they included more content-related information,” according to Gilkson.

Another interesting finding is that when the gender of the email sender was unknown, the “recipients were more likely to assume that the email was sent by a woman if it included a smiley,” the press release states.

The good news is that apparently the emoji-demerit only applies when you communicate with someone for the first time, Gilkson said. So while you’re probably safer skipping the smiley in a “nice to e-meet you!” message, you can still use them to spruce up communication with contacts you already know.

These findings add to the ongoing confusion that is communication in the digital age. If you want to learn more about how to navigate talking on-and-offline in the era of emoji, go here, and you can read the full press release for the study here.