A recent report from Experian found that 56% of brands using emojis saw a higher open rate on their email campaigns. Emojis in subject lines are a great tool for several reasons, firstly are great space savers, you are usually quite limited to subject lines, particularly on mobile, so using an emoji can say a lot without taking up too much room.
Another great benefit of using emojis is to convey some sort of emotion within your emails or newsletters. Depending on your market and target audience, emojis can help attract your audience demographic, with millennials using them very frequently, therefore emojis may help you hit a younger market that you have not yet succeeded in.
Finally, emojis may help you to add more fun and lighthearted tone of voice to your email subject lines, which will ultimately make the users feel happier and more excited by your emails.
Source: Campaign Monitor (https://www.campaignmonitor.com/blog/email-marketing/2019/04/the-real-scoop-on-email-emoji-in-subject-lines)