Based on the word "emoji" this domain name has clear connotations to the online and social media world.
The word "EmojiU" contains only six characters and four syllables. Successful brands using four syllable names include Airbnb, ESPN and Unilever.
Emojiu.com is a dot-com domain. Dot com domains are the most prestigious top-level-domain in the world, used by famous websites like youtube.com. When most people think of a website, they think of a dot-com.