Unlicensed JIRA users can be mentioned but do not received emails

Summary

Whenever a user does not have access to JIRA Software or Core, and they are mentioned on an issue, they do not receive notifications for that issue.

Steps to Reproduce

1. Create a user without any application access
2. Create a notification scheme that includes this user (we tested by allowing browse projects permission and notification through a user custom field and also through watchers field)
3. Add user to that issue as a watcher or using a custom field
4. Make sure the user has browse permission access to that issue
5. Try to generate notification
6. No Notification is sent, neither information is thrown on outgoing mail log

Expected Results

The users who are mentioned on a JIRA issue but have no application access should receive notifications on the issues they are mentioned in.

Actual Results

They receive no notifications at all