We are phasing out Zendesk. Please see Discourse instead: https://community.getmailspring.com/t/using-emoji-in-emails/257
To insert emoji into your message, click the emoji icon at the bottom of the message window and choose from the menu.
You can also type :emoji: with the colons and the emoji short names, Slack-style.
And, yes, both :poop: and :hankey: work for the poop emoji. 😅