Problem: You collect service requests into Jira or JSM and would like to notify users who submitted them once their tickets status is changing. Users are external and they're not known to Jira.
Solution: First of all, make sure that you're storing user email (mandatory) and users name (optionally) when creating Jira tickets. An easy and elegant way to achieve that is to use Raley IntakeForms addon to configure your form and collect all the necessary data. Once you have your users data attached to a Jira ticket, create a Notification in Raley like in the screenshot below:
Note, that this notification will work whenever issue is project MFP is transitioned from "In Progress" to Closed, Done or Escalated statuses.
You can choose several statuses in both FROM and TO fields and the notification will work if current issue status before was one of the statuses specified in FROM and the status after is one of the values specified in field TO.
In Email(s) input you specify the code of your Jira custom field which contains user's email address.