They have already invaded our text messages. And emojis are now taking over our email subject lines. From smiley faces to suns and small animals, these everyday life pictograms are now a way to communicate.
Adding a symbol in an email subject line is not new, but since most email service providers support them, they have become a common practice to make messages stand out in a crowded inbox.
Fun, childish, effective, irritating… many qualifiers have been used to describe emojis. But their popularity is undeniable. You certainly have your own opinion on the subject. According to Marketing Profs, 64% of people of all ages say they like emojis, while 29% are neutral and 6% don’t like them. The percentage in favor of emojis rises to 70% among audiences aged between 14 to 24 years old.
A good way of validating if the use of emojis will have a positive impact on your results is to test them. Send a version of your message with an emoji and one version without, and compare the results. According to an Experian study, 56% of brands that use emojis in their email subject lines get a higher open rate.
Although the majority of people are favorable to seeing icons appear in their inbox, they have to be used wisely. When should we include an emoji in an email subject line? The answer is simple – only when it’s logical and suitable.
Don’t use an emoji only because you have nothing interesting to say. And including an emoji doesn’t automatically make your subject line good either. Use it to support your message and add a playful touch. Be careful however not to overload your subject with too many images. Don’t use them all the time either, as your recipients might get bored. Instead, surprise them from time to time.
Unfortunately, emojis are not suitable for every audience. Make sure that the use of emojis fits the tone of your organization, and of your message.
If, for example, you work for a financial company with a more conservative tone, perhaps it’s better to avoid emojis as they could be perceived as unprofessional or even as spam. Also, take into consideration your international recipients. Some images could be perceived differently according to the culture, country or language of the recipient.
Know that emojis are not supported everywhere and that it’s not all the symbols that will necessarily be displayed. It’s crucial that you perform several tests before sending your email because it is quite possible that your recipient will see an empty square instead of the heart you have planned to show.
Moreover, there is no guarantee that these emails will be well received. Each domain, service and anti-spam filter is configured differently, or almost. So each one of your recipients may therefore have a different set of rules that will either accept special characters in the subject line or not.
Here is a table that shows if symbols are supported in email subject lines for the major email clients.
Source : https://www.campaignmonitor.com/dev-resources/will-it-work/symbols/
Ultimately, the golden rule that prevails when sending emails is always the same: Test… And have fun! 
