Based on my testing so far, it seems that if Jira receives an e-mail from an address that's not associated with a user and automatic creation of users from e-mails is disabled, Jira just silently ignores it (as opposed to sending a reply along on the lines of, "Sorry, you need to have an account to submit a ticket."). Is that true? Can it be set to send some kind of reply?
Thanks,
Chaz