Which emojis—the small icons used to convey emotions, things, and ideas—are marketers employing most in email subject lines?

To find out, MailChimp examined 214,000 campaigns with emojis in the subject line sent by brands since February 2015, when the platform officially added support for them.

The registered trademark is the most used emoji by marketers in email subject lines, the analysis found.

The big-eyed happy emoji is the next most-used, followed by the smiley with heart eyes, the heart, and the standard smiley face.

The researchers also mapped which emojis are used most together in email subject lines.

In the following visualization, emojis that are closer are used together more frequently, and emojis that are larger are more popular pairing partners.

About the research: The report was based on data from 214,000 campaigns with emojis in the subject line sent by brands since February 2015.