It’s possible to use symbols in your emails, and they can be a fun way to enhance your communication. However, they should be used with caution. Symbols in subject lines are not supported by all email clients and not all symbols are universally supported, so be sure to test thoroughly before using them.
Also remember that subject lines are not HTML code so you can't use entities as you would have in the actual email content. You need to copy the symbol from a website or document and paste it into subject line field.
You can try using symbols from websites such as fsymbols.com. Also, remember to have your email project/folder encoded with UTF-8 to make this work. This is set under account + project admin.
Keep in mind that if a character isn’t supported in the email client, the recipient will see a ☐ character instead or the word ‘emoji’. Your symbol may also be substituted to another symbol. In our own tests, symbols does not automatically end up in spam folders, but there are indications of some email clients being sensitive to those kind of subject lines. So, test, test and test!
Below is a sheet of current client support:
*Emoji is a special set of images and emoticons