We have a mix of projects (Jira Service Management in this case), some of which have dedicated emails to open tickets (and they have very helpful email logs), but we have some projects that just use the generic jira@<our-site> email for responding to existing tickets (they can only use the portal to create tickets, but use email to comment on existing tickets).
I'm trying to track down a couple emails that were sent and delivered to jira@<our-site>, but didn't result in the comment being added to the ticket.