According to 9to5Google, Google has been working on incorporating emoji reactions into Gmail. Other email services, like Apple Mail and Microsoft Outlook, already have emoji reactions for users to add to their emails.
On the Android blog, TheSpAndroid, user AssembleDebug found that emojis are already available in mobile Gmail -- to a certain extent. Users can find an emoji reaction button next to the reply button and choose from a predefined list of reactions.
But if users tap the "+" button next to the emojis, they can choose any emoji to include as a reaction option. If the email recipient's email address is not Gmail, they won't see sent reactions on the email and will instead receive a separate message with enlarged emojis the sender sent.
So, using emojis in Gmail will operate under a level of exclusivity, as emojis won't be compatible with other email service providers. According to AssembleDebug, users cannot send more than 20 emojis in one message, and users cannot use emojis to react to emails sent to a larger number of recipients.
Additionally, if someone is BCC'd on an email, they cannot react to that message with emojis.
Emoji reactions should be widely available in the Gmail app on Android and iOS soon. Google has not publicly announced this feature, and when asked about it, the company told The Verge to "stay tuned" and added a winking face, open-palm hand, and drums emojis.