Non JIRA Users
There are two kinds of non-JIRA user:
Non-JIRA 'Account Holder' without Right To Use
This kind of user needs a JIRA account created, but does not require 'Right To Use' therefore is not interactive, therefore does not contribute to seat count. Being a JIRA user, incoming mail will be associated with that user, and so that user account must have sufficient privileges in the target project to create/update issues. JEMH can do this by adding people to an auto-join group. Management of the Roles in target projects is something the JIRA administrator must do.
Pro: Can use JIRA security
Con: Can clutter a user repository with redundant, seldom used accounts
Non-JIRA 'Email Only' User
This flavour of non-JIRA user has no account, does not require any special groups and not being interactive, does not contribute to seat count. Incoming mail is 'intercepted', email addresses are extracted and stored in standard JIRA custom fields. JEMH requires a 'proxy' default reporter to be defined, this is the user that the issue will be created 'as'. The address of this user should not be a valid incoming mailbox address, in fact this addressee can be blacklisted within the JEMH Event Listener to stop any 'useless' notifications.
Pro: Doesn't clutter a user repository with redundant, seldom used accounts
Con: Can't use JIRA security.