Currently, when an email have emoticons in it, the issue creation will be rejected by JIRA Service Desk if MySQL is used as the JIRA database.
In the log, the following error should be seen:
This is because email emoticons use 4-byte characters, while MySQL doesn't support this:
JIRA Service Desk should auto render the emoticons as text, so that issues will be successfully created.
This will also work if 4-byte characters are supported in MySQL.
Switch to a different type of supported databases: Postgre, MS SQL, or Oracle.