There are a variety of emails you can use to send an email to the Royals.

His Majesty: king@eastkingdom.org
Her Majesty: queen@eastkingdom.org
Their Majesties: trm@eastkingdom.org

His Highness: prince@eastkingdom.org
Her Highness: princess@eastkingdom.org
Their Highness: trh@eastkingdom.org