For email related to work, the use of the smiley or any type of emoji does not have a positive effect, but it can lead to negative thoughts about you. In one study it has been claimed.

"Our results provide the information for the first time that unlike actual smiles, Smiley does not have a sense of warmth, but negative perception about your abilities is created," said Ela Glickson, a postgraduate Fellow of Ben Gurion University of Nigve of Israel. Smiley can not replace a smile in a formal email. " 

The researchers used several experiments. In this experiment 549 people from 29 different countries took part. This research has been published in the journal 'Social Psychology and Personality Science'.

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