In a world where face-to-face conversations are becoming increasingly rare, it may be tempting to try to soften the blow of a harsh message or a difficult request with a "smiley".
However, the digital image of a smiling face can have the opposite effect to an actual smile for the person on the receiving end, researchers have found.
Emoji are used six billion times a day and have been described as the fastest-growing language in history.
Now it seems the sender could be making themselves seem less competent.
Academics warned that peppering an email with emoji could harm your job prospects by making colleagues less likely to share information with you.
The effect can be so damaging that people are advised to avoid them at work altogether.
Dr Ella Glikson, an expert in business and management at Ben-Gurion University of the Negev in Israel, said: "Our findings provide evidence that - contrary to actual smiles - smileys do not increase perceptions of warmth and actually decrease perceptions of competence."
The study, published in Social Psychological and Personality Science, was based on a series of experiments involving 549 people from 29 different countries.