What is an emoji?
Emoji:

a small digital image or icon used to express an idea or emotion.

A study published in the journal Social Psychological and Personality Science suggests, including a smiley emoticon or an emoji, in a work email may have some people thinking you are unprofessional.

So, should you be using emoticons or emojis in workplace communications?

One Reddit thread asked this question,
         Why: People who refuse to use emojis?

Maybe it is because different emojis can be interrupted in many ways.
Insider Tech published a video about Emojis that everyone is using wrong. 

On the one hand, emojis can soften an otherwise concerning or short email and allows the sender to show more emotion in an otherwise cold statement. On the other hand, they can also come across as less competent and or inappropriate. It’s important to keep in mind, if you are receiving a smiley face, don’t judge. It really shouldn’t be a mark of competence in any way.

Perhaps Hot_mention_9337 answered it best.