My previous service desk had email integration in the responses. You were able to select a user or type an email address in both the To and CC fields. I find that this is lacking in JIRA Service Desk, and would like to find out if we can add that functionality.
In the environment I'm using Service Desk in, clients will often email in their tickets and CC relevant parties. If those parties are left out of the ticket or responses, then we can't ensure that all the right people have the latest information.
I've also installed CRM for JIRA, but I'm not sure that this will be useful in handling email tickets, or ticket responses.